Baffling Fuel Injector Faults and Misfires: need help!

Ok, ready to enter my nightmare? Bought my first P-car a few months ago: a 2002 C4 Cab with 98.5k miles. Car came with an intermittent #5 misfire which the previous owner and indy mechanic were highly confident was the result of a bad DME (they�d already tried replacing the injectors and testing the harness). Previous owner had purchased a used DME, but wasn�t able to get it programmed because the nearest dealer was ~4 hours away and decided to sell the car instead. Knowing I�d have to replace the computer also resulted in a pretty good discount when negotiating the vehicle price. Shipped the car home and as expected, #5 cylinder fuel injector electrical fault (P205) and misfire (P305) intermittent codes that got worse as the engine warmed up. Step one: pulled the DME and immobilizer and shipped them down to Specialized ECU Repair in Florida for diagnostics. They insisted my ECU was perfectly fine based on their bench tests and claimed it ran fine in their test car (although I don�t know how extensively they tested it considering my experience was that the problem was much less frequent when the engine was cold). They offered to program and ship me one of their �rebuilt� ECUs for $1000, but if it wasn�t a fix there was a 30% restocking fee (are you kidding me?!). I opted to have them send my original DME back. Next, thinking Specialized ECU might be right and my DME was fine after all, I took the car to the local indy P-car expert and we dove deep on trying to test everything else we could think of: -Swap #5 and #6 fuel injectors? Check, problem stayed at cylinder 5 (injectors 4, 5, and 6 were all replaced in December of 2017, injectors 1-3 are older). -Resistance on the fuel injectors? Check, 12.5ohms on all six injectors. -Voltage at the injectors remains constant, no voltage drop to the DME on either the ground or positive sides -Wiring harness? Electrically checked at the DME connector and at the components themselves to eliminate the harness. -Connectors between the harness and the fuel injectors? Checked. -Clean the Mass Air Flow sensor (a possible fix we discovered on a Rennlist thread where a user had weird misfires and fixed them by replacing his MAF, but he noted an improvement simply by cleaning it)? No change -Bypass the usual wire and power the injector directly from the battery? Check. -Check for AC current leaking out of the alternator? Check. ...All with no fix. At this point we decided to go back to the �bad ECU� theory. I ordered a used DME off eBay from a car that�d been in a front-end collision (figured the donor ECU should be fine considering its placement behind the rear seats) for $120 (definitely beats $3k for a DME directly from Porsche!) and had our local Porsche dealership program it. Here�s where it gets weirder� On ECU �B� (for the sake of clarity I�ll call the original one �A� and this one �B�) the problems related to cylinder #5 went away! Except� now cylinder #1, which had never previously given us any problems at all, was throwing P201 (Injector Fault) and P301 (#1 cylinder misfire) codes worse than we�d ever had with ECU A and cylinder 5! They were so bad that as the engine warmed up the computer gave up on cylinder #1 altogether and stopped sending signals to that fuel injector (we hooked up noid lights to the #1 and #5 fuel injector circuits to monitor the signals and the #1 eventually just went out altogether)!! We checked the resistance in the wiring harness to the #1 injector: no problems there. Then we swapped back to ECU A: sure enough, cylinder #5 started misfiring and cylinder #1 worked great. At this point we were thinking that, unlikely as it seems, we�d replaced a DME with a bad #5 injector driver with a DME with a bad #1 injector driver. We returned ECU B to eBay, ordered ECU "C" from another donor car, and once again had it programmed by the local dealership. Installed it in the car and� Exactly the same behavior as ECU B: P201 and P301 codes eventually resulting in a full shutdown of the #1 injector and no problems at all in cylinder #5. What are the odds that, on top of getting two bad computers in a row to replace our original one, both ECUs B and C would have exactly the same problem on the same cylinder??? We�re stumped. The only thing we can think of that we haven�t tried is to swap the #1 and #2 injectors to definitively rule out the #1 injector itself (which is a long shot at best considering it runs fine with ECU A). What else could be causing this? We�ve scoured the forums here and over at Pelican and we can�t find anything remotely similar or that we haven�t already tried, especially not anything that would make sense of the misbehaving cylinders reliably swapping between #1 and #5 depending on which computer is installed. Any ideas or advice would be greatly appreciated!!!

And this is why the technicians get paid the big bucks. What's your fuel pressure at the rail? How old are your coils and plugs? Maybe start with ECU "A" and this time swap the coil packs around.

Coils would have been my first thought. I'm surprised no one has even mentioned this...? Make sure your coil wire on #5 is fully seated with a click. Check the wiring for damage, mice love to chew on wires.

Do you know if the injectors are genuine Porsche parts and the right parts for your MY? Sounds like an electrical problem to me. The P0201 and P0205 are complaining that the DME has detected OPEN circuits on those injectors. The injectors get +12v from the same junction as the coils and there are no other connectors involves (except the injector connectors). However, the injectors gets the ground from the DME via the x59/1 connector 0- one of the two big round connectors on the right side of the engine bay. I believe it's the top one but please verify yourself.. You can spray the pins on both sides with Deoxit and check again. The pins are 5, 6, 7, 19, 20, 21 for cyl #1-6, respectively.

If you can do most of the diagnosis yourself by start swapping out existing parts then you could save a bunch of money. At this point everything points to all 3 DMEs being bad but as you stated, the chances are low that that is actually what's happening. I would start a new systematic diagnosis. Do what you did first and then keep going by swapping out and testing with other injectors and/or the DME. Also would have a close look at the coils and plugs but only do it in a systematic way or else you'll loose site of what the results are. Also, if the spark plugs are put might as well put a borescope down the cylinders and have quick look.

I'm away from home for work at the moment, so I won't be able to check the service records until tomorrow or Thursday, but I know all new plugs were installed this December and I believe the coils were also replaced within the last couple of years. I'm also going to check with my mechanic to see what swapping around he's already tried that I may have forgotten to write earlier. The thing we keep coming back to is "if the problem was _____component, why would it stop/start misbehaving depending on which DME is installed?" In the meantime, please keep the ideas flowing!

Just heard back from my mechanic on one of my questions. According to his research, there are three conditions that'll trigger a P020_ fault: 1. Incorrect resistance in the injector (all six are identical at 12.5ohm in our testing). 2. No voltage signal when the DME reads it through the injector coil winding 3. A short-to-ground causing the injector to stay open (which we should have detected in all of our harness testing!) I'll update all of you on what happens when we swap the #1 and #2 injectors. If the problem doesn't follow the injector, I'm wondering if we should try swapping the #1 and #2 coils (Idea being that the #5 cylinder problems might be the result of ECU A being bad and the #1 cylinder problems might be legitimate issues that the bad ECU A wasn't detecting but ECUs B and C did detect. It's a stretch, but not any more of a stretch than the odds of three bad DMEs and 2/3 of them having the same fault).

This may be a long shot, but might be easier than swapping injectors. The shade tree version of trouble shooting would be installing any one of the three ECUs with a same M-Y 996 and checking against a working ECU and car. Would your Indy have a source? Anything from eBay would be suspect. Could be where previous owner picked his up.

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Testing an ECU in another car (even same model year and version) would require either reprogramming the ECU to match the other car ($$$ and can only be done by a dealer or specialist like that outfit in FL) or would require swapping all three of the ECU, immobilizer, and ignition switch between cars to have a matched set. Even considering that, it'd be something we'd consider if we had access to another car and permission to test it, but my indy doesn't have any 996 clients that he thinks would be willing to help like that. ECU A is original to the car, B and C are the ones I obtained from eBay (from a different seller than the one the previous owner obtained the one he couldn't get programmed).

Just got back from visiting the shop. He got bogged down on another car today, so he hasn't had a chance to swap the #1 and #2 injectors yet, but we spent a little time talking about what to try next if that doesn't work. One of the things I kept circling back to as a result of this thread is the possibility that there might be an issue with the coils. Despite the many, many problems he's fixed with coils over time, he can't see any way how a bad coil would cause these faults because of the three P020_ trigger conditions I mentioned earlier. As @Ahsai mentioned the coils and injectors all share the same +12v source, but the P020_ fault is being sensed by the DME on the ground side of the circuit and during our original testing with ECU A we powered the #5 injector straight from the battery to bypass everything on that +12v circuit. Nevertheless, despite everything seeming to point to three bad DMEs in a row, I just can't wrap my head around the odds of that. So, after we try swapping the #1 and #2 injectors on ECU C, the next thing we're going to try is swapping the #1 and #2 coils to see if the problem chases a particular coil. Two other things of note: 1. Remember how I said I was pretty sure the coils had all been replaced recently? Well.... we're not so sure. I've got an invoice from the shop in Montana that'd been taking care of the car for the previous two owners that claims all six coils were replaced in July of 2016, but the coils on the car don't match the part numbers on the invoice! The invoice is for 99760210402, the coils on car are Berus but a different part number (sorry, don't have it written). My mechanic thinks that either these are the original coils and they were never replaced or these coils were old stock and the MT shop made a mistake when writing the invoice. 2. On a related note, I discovered that I'd omitted something from the original diagnostic regimen: Before we started replacing ECUs we replaced the #5 coil and that new coil is still on #5 even though it hasn't seemed to make any difference.

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Exactly. When they swap the injectors, they should also note the p/n and cross check. Your coils may be due but I highly doubt they will fix your injector error codes. Also, don't forget my comments about the x59 connectors.

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Excellent idea to check the injector part numbers, especially after this business with the coils not matching the paperwork! And, forgive me, but I'm not enough of a car guy to recognize the acronyms: FRA, RKAT, AFR?

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Never mind those FRA comment. i got your case mixed up with another thread

Sounds like you and your Tech are now going in circles. Y'all seem to be competent, but may be too emotionally attached to the problem to be objective. Might want to step back, take a breath a fresh air, and try a new approach Instead of running until you get the code, then doing the usual fault tree diagnosis. Look at the overall picture. 1. How intermittent is it 0% to 100%? 2..When you say it gets worse when hot, how much worse scale of 0- 10 ? 3. Can you manipulate it ? Make it better or worse by wiggling things, tapping on things? 4. When the problem starts, does it stay? If not , what makes it go away? 5. Has the engine ever been out of the car? Think of the DME as Big Smart Grounding Device, it controls injectors and coils and actuators by grounding them. Yes it has power to it, but does all the high current through ground. Make sure the ground points are good, all of them. Check them for tightness, then loosen and clean them and re-torque. GP9 and GP8 are the main ones for the DME, but also check the ground-strap to engine, and the battery to chassis cable. It will all make sense once you find the problem, and the really tough ones usually end up being something simple, but hard to put your finger on.

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Haha, yes, going in circles is definitely how it feels!! A code like P020_ is supposed to be related to one of three components (DME, Injector, and the wiring between them, particularly the ground), so when we've independently eliminated all three it's definitely vexing. There have been a number of ~week long pauses in the work for that very reason or because we've been waiting on something (parts, programming, etc), but no such clarity has emerged. As for your questions... (for the sake of discussion let's assume all of these are answered in relation to ECU A and cylinder #5 unless noted because that's where I have more data) -On a cold day, say<~30F, it is much more rare, sometimes seeming to be close to 0% until the engine really warms up. After that it's a noticeable, fairly constant low-grade misfire. -On a warmer day, say 50-65F, a few occasional (20%) misfires are noted within the first few minutes after startup. Once the engine warms up it gets to the point of seeming to misfire on nearly every rotation and each misfire is more noticeable (not huge, but not something that can be mistaken for road imperfections like the infrequent misfires on a lukewarm engine on a cold day). -On ECUs B and C where the problem occurs with cylinder #1 instead of #5, the misfires start within a couple of minutes of startup even on a cool day and by the time the engine warms up power is cut to the #1 injector altogether and it becomes a five cylinder engine (this is evidenced by the ride and by the noid light extinguishing altogether instead of flickering with DME signals to the injector). The problem gets worse at higher engine speeds (as in: when the engine is still warming up and it's in the 20% misfire range at 2000-3000rpm, it can reliably be bumped up to 70%+ by throttling up to 3500-4500+rpm). Beyond that, except for moving the problem by switching ECUs, we have not noted any variation even when changing the power source to the injector or bypassing the wire from the DME to the injector. As a caveat on the above answer: since the problem has required a warmer engine, nearly all of our testing has been road testing rather than running the car stationary in the shop, so there has been very little wiggling and tapping tried. Once it starts, it can be somewhat calmed briefly by coasting the car (fuel cutout to all injectors) and then running at very low load, but that doesn't last long and comes back quickly when even moderate power is applied. IMS was done at 93k miles (August 2016), so it would have been dropped then, right? Sorry, I'm new to P-cars and I'm still learning what requires a drop and what doesn't. Beyond that, no, I'm not seeing anything in the service records I have going back to 2013/66k miles that might imply an engine drop. Sounds like a handful of worthwhile and relatively-easy items to test! Thanks!

Throughout all this, and I know that just throwing in parts is never a really good idea, but to start to eliminate some things have your mechanic install NEW coils and NEW spark plugs now. You have to start getting a baseline for things. Get pictures of the condition of each cylinder spark plug and post. You can tell a lot about a cylinder by how the spark plug looks.

I find the above strange...anyone else? Unless this is a weak point for these ECUs what's the odds that two would be failed in the same manner? In addition you didn't believe Specialized on ECU A? I'm with DB above plugs and coils inspect as they come off. Verify injectors are fresh and of proper type(I might have missed if this already done). PT3 above with his "it's usually the simple things" post is excellent information, as well. Good Luck.

You also have to remember that in the scientific world, electron flow is actually opposite of what is commonly known as conventional current flow, in that electrons flow from negative battery post toward the positive post. So for the injector to work, the electrons flow from the negative battery post, into the metal chassis, then through GP9 and GP8 and into the DME.Then out of the DME to inj.#1 or inj. #5 ect. and to the 12v splice and back to the battery positive. Since injectors require the highest amount of electrons to work ( of the DME curcuits), if there is not enough flow of electrons through GP9 or GP8 at high load (high injection time) the injectors will be erratic. There could be slight differences in the internal resistance paths in the 3 different DME's that if there were enough electron flow these slight differences would not effect the injector function. It's also common knowledge that bad ground point connections get worse with heat or load/usage time, and can cause damage to DME curcuits. Of course these are just theories, and could be enlightening if it proves to be the problem..

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Yeah, in a past life, before entering management, I was a railroad electrician so I'm aware of electricity. I agree wholehearted with the simple things theory you are promoting i.e. your connection checking/cleaning suggestions. I saw way too many "hot shot" locomotive troubleshooters run around in circles convinced the solid state devices they had changed numerous times must all have been bad and when left for me to fix I found a broken wire on a terminal board that was hiding behind a cover in about 20 minutes after a week lost to the "experts". Supervisor thought I was lying to him when I told him it was fixed and what should I do now. Simple things...

Sounds to me the easiest thing to do would be to connect one end of the jumper cable to the negative battery post and the other end to the engine block and see what happens.

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Doing that would not help the current flow through the DME and injectors.

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Ok then find the pin for the DME ground and extend it to the battery negative. That should do it. What I'm trying to get to is to make sure the supplied ground is good.

Seen many electrical issues solved by a better ground.

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Gotcha, that would work, the DME has several ground wires..

That is very odd indeed. Based purely on what you have written, it sure seems like an electrical problem, and if I had to guess, something with a bad electrical connection, which could be a ground, a high resistance connection outside of the ground, or maybe even a rodent that ate part of your wiring harness. Sorry I can't be much more help, but I sure don't think you have three bad ECU's. It sounds like you have three good ones.

Thanks for the continued input, everyone! I emailed my indy late last night with some of your thoughts and a handful of other things I learned during many, many hours of searching and reading on here (including some excellent info @Porschetech3 gave to users in some other threads, such as the cat protection logic in the DME that would explain why the #1 injector is getting shut off completely!), but I haven't heard back from him about what he was able to try today or the results. Based on the growing consensus here I'm getting more and more confident that we need to focus our efforts on looking for issues elsewhere in the electrical system beyond the fuel injector circuits we've spent so much time on. Besides all this great electrical discussion, the two components that are still on my radar are the coils and the MAF. One interesting thing that turned up in my research was the idea to do a test drive with the MAF unplugged: theory being that if the MAF is the culprit then the misfire should go away without any MAF input data (engine would be less powerful during the test, of course, but if the misfire persists we'd be able to scratch out the "bad MAF" theory). I'll keep you updated as things develop!

Just heard back from my Indy. Here's what he said (slightly edited for clarity, such as using our ECU A-C nomenclature): Besides scoping the injector signal waveform, any ideas? I suggested again that we try the MAF-unplugged test, but that's just a shot in the dark. Also suggested @Ahsai 's idea of disconnecting/cleaning the X59 connectors. Like @Porschetech3 I'm concerned that we might be fixating on the DME and not thinking outside of the box enough, but that test of running new grounds to the DME seems like it would have eliminated a lot of possibilities.

Stopped by the mechanic yesterday. Apparently he never got my reply a few days ago (must have been a Gmail glitch because it's also not anywhere to be found in my sent or draft items), so we spent some time working on a a gameplan. We're going to: -Replace a cam sensor that's leaking oil (we've tried cleaning and reinstalling it already, but the leak is back). Shouldn't make any difference for our misfires, but it still needs doing and what's weird about it is that it's somehow wicking oil into the X59 connector via the harness wiring. Oil is an insulator, so it shouldn't (?) make any difference for our misfire issues, but it's still weird. We'll re-clean the X59 if more oil has found its way in there since when we first cleaned the cam sensor a few weeks ago. -Replace the other four coils. We've already done our problem cylinders #1 and #5, and we're not expecting this to make any difference for our misfires, but it makes sense to do the rest just to have them done. I'll confess I'm getting frustrated enough that I'm more willing to throw money at the thing just in the hopes that something would happen, especially as we're getting into top-down weather and my mechanic has put more miles on the thing than I have!). -Swap the #1 and #2 injectors to see if the problem moves with ECU C installed -Test drive it with the MAF unplugged -Record the waveforms of the fuel injector signal pulses from the ECU -And, lastly, if none of the above makes any difference, our last idea apart from a 4th DME would be to start unplugging/examining/cleaning every electrical connector we can get our hands on even if it doesn't seem remotely related to the problems we've been having. I've already told you that he's tried bypassing the DME grounds, but I didn't know until yesterday that he's also cleaned and bypassed the main engine ground as well. Any other out-of-the-box ideas we should consider? Is there any conceivable way that the oil in the harness from the cam sensor could be causing all of this despite oil being an insulator?

First off, when I start chasing any issues, I stop and verify mechanicals immediately. I'd say a running compression test is in order for this one, before you chase your tail any further. I have seen injector codes and misfires from cylinders that had no injector, or coil faults, but had mechanical issues on that same cylinder. A running compression test is the only way to go here, static tests won't show the issues.

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The reason we haven't considered a compression test is that each of the "misbehaving" cylinders function flawlessly with one DME or the other. ECU A and cylinder #1 runs great (but cylinder #5 has problems after a while), ECU C and cylinder #5 runs great (but #1 starts acting up shortly after engine start). Wouldn't a mechanical issue with a given cylinder misbehave regardless of which computer is installed?

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I had a Chrysler V6 that had been to 2 other shops for a random misfire on a specific cylinder issue come to me. You would have sworn it was an ignition issue from the "feel" of the misfire. Of course, the other shops had covered all of those basics. A static compression test yielded normal results. A running compression test however would show an anomaly every time the misfire occurred. Long story short the engine had a valve guide issue that was hanging a valve intermittently causing the skip. What bothers me with your scenario though is the P0201 and P0205 codes. These are circuit codes and will not be set from a misfiring cylinder for any reason other than something related to the injector circuit. How I think you could best isolate this misfire further is to get an injector connector, and make a separate sub harness to run to cylinder 1 injector and all the way back to the DME. It doesn't have to be pretty because this is purely for testing purposes. I would pull the 2 pins from the DME connector and replace with my sub harness with the correct pins for the DME on the ground side and a known good +12volt on the other side and see if the issue is resolved. If so, go back to the original wiring and scope the injector on both sides and see if you are losing the power side or the switched ground side. Once you determine which is failing you now get to hunt and find where the harness is wounded. I know of some techs that think the separate harness is an acceptable permanent repair, but I personally dislike that because if the damage is caused by something like a chafed bracket there is likely going to be other damaged circuits in the future. Better to find it now and keep it from happening again. If your misfire and injector codes are still there after this, you need to test the grounds to the DME itself and verify they are good all the way to the DME if you have isolated the failure to the switched ground side. Once that's done, you have pretty much effectively ruled out everything but the DME itself.

That's a classic.. Same thing happens with a lifter in these engines. Yes, if one ECU works fine, and the other doesn't;t, then it doesn't sound mechanical... Never hurts to check, though.

Have you scoped the fuel injectors? How do the waveforms look?

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Thanks Matt! What you describe sounds a lot like the bypassing we've already done, but I forwarded your suggestion to him anyway just in case there's some tidbit that we've somehow missed or overlooked.

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It's on our list! My post this morning (~8:30 your time in TX) was roughly in the order we're planning on doing things, so when we get to the scoping stage I'll definitely let you know. I'll try to get pictures of the waveforms to post on here if at all possible!

Whilst I am not suggesting it's your issue based on the misfires changing with the ECU. I had a persistent misfire that was ok when cold but would trigger when hot or revved that turned out being a sticking valve lifter which totally resolved the issue. looking at the service records that came with the car it was clear the previous owner and various shops had tried to fix the misfire with new coils, plugs and sensors to no avail. Lifters do stick on 996.2 3.6 engines, you replace them with a revised part.

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Fascinating: I'd heard only the Turbos had trouble with sticking lifters! That's good to know even if it's not related to my current issue. Thanks!

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Great. Looking forward to seeing it.

Just heard back from my indy: No joy from our cam sensor/four coils/injector swap/MAF-unplugged work. Yesterday he hooked up the his scope and recorded three different runs measuring the fuel injector signals from ECU A to cylinder 5 and to a known-good cylinder. He didn't include any pictures, but here's what he said: I've emailed him asking a couple of clarifying questions such as where in the circuit the signal was being measured, but it sounds like whenever there's a misfire it's because the ECU isn't sending a signal to the injector at all. I've asked him to test ECU C and cylinder #1, but I'm not sure when he'll get a chance because they've got a full case load. If the results are the same with ECU C (no injector signal altogether), are we back to the "bad ECU" theory with three bad ECUs in a row? Considering those crazy odds, is there anything else that would make sense of this? I'm tempted to send ECU C down to Specialized ECU in Florida for testing (it shouldn't be able to pass their tests like ECU A did because it causes misfires much more quickly), but even if they confirm the problem repairing/replacing it through them would be more expensive than buying yet another eBay DME and having it programmed.

Haven't heard back from my indy on those questions yet, but I went ahead and ordered yet-another DME from eBay. It has a 30-day return window and will take a few days to arrive, so I figured it would make sense to get that process moving while we try to decide if that's the direction we should go. Any ideas? I'm thinking of posting a thread in the East US Region board asking if there's anyone who'd be willing to let us borrow their car for a couple of days so we could try swapping a known-good DME (+ immobilizer + key: I think you need all three) into the car, but I'm not optimistic we'll get any volunteers.

Got some answers from the indy. And pictures! For the sake of clarity: all four images below are with ECU A (the original), which is the one that is more intermittent about the cylinder #5 misfires (yellow line) and has no problems with cylinder #1 (green line). I'm hoping he'll have a chance to scope it again with ECU C installed, where we'd expect to see cylinder #5 running smoothly and cylinder #1 barely firing at all.

That's just crazy !! The odds for having 3 bad DME's is unheard of..That said it looks to me your problem. I was specialized in drivability for over 20 years for FoMoCo and was awarded CTP's top Technician award for the southeast region for many years in a row during the advent of electronic fuel injection, and then for 10 years with Mitsubishi and then 10 years with Porsche and can say that I have never seen 3 failed DME's /ECU's in row like that. I can also say that 90% of the failed DME's/ECU's were due to wiring shorts that damaged them, or bad engine grounds that sent starter ground amperage through them on startup instead of through the ground cable.Your starter is spinning fine/strong/fast right? Since you have now gone through all the ground connections and tested, cleaned and tightened them, maybe you will have no more DME failures and one more good one will do the trick.

Shawn, I thought I would try to get back to you before you spent more money on having your newest DME coded to your Porsche. You have done an extensive amount of work to your car trying to figure out the cause of the misfire, but what I'm proposing will take even more. My thinking is this, since you have had this fault ever since you brought home your car and that your 996 had the IMS bearing done just 2,000 miles before you took ownership the fault may lie in the installation of your new bearing. A mechanic with no previous knowledge of the process of bearing replacement might have been surprised by the weight of the dual mass flywheel. There is a chance that he dropped or some how damaged the toothed portion of the wheel when dismanteling. Since cylinders 1 and 5 fire first and last in the fireing order that may account for both misfires showing up at that point on the fly wheel. Also the fact that the misfires are more pronunced when heated up, the crankshaft position sensor would have a harder time picking up a signal from bent teeth throught hot air as that is denser than cold air. So with all that being said I'm not sure which direction you would want to take, or which is less expensive. Examining the flywheel is a big job, but you may want to check everything else associated with that job since the car is new to you. The flywheels do wear out and I think they recommend replacement every other clutch job. Thats about all, A. P.

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. Thi� is a good thought and I had considered the possibility of a damaged flywheel teeth but I discounted it due to missfires are not on paired cylinders.. On the m96 cylinders 1 and 4 use the same teeth of the flywheel so they would be equally likely to missfire. Takes 2revolutions to fire all 6 cylinders.

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Yeah, thanks for the info. Kind of a reach not sure of flywheel layout. Hope a fourth ECU does the trick.

FWIW I have seen a bad dual mass flywheel lead to random misfires on several occasions. Usually it�s not one cylinder, but it could be. If the dampening of the second mass is less than adequate, a lot of odd things happen, especially at idle and low speed.

Is the injector commanded by the crank sensor on these cars though? Most vehicles it is synced up to the cam sensor as the injector can only fire once during the intake stroke, while the ignition is typically fired twice with one as a wasted spark triggered off of the crank sensor.

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It is not a wasted spark system, It is a sequential spark and sequential injection system. The crank sensor sends precise information on crank angle and speed to the DME, the DME uses cam position signal to determine which injector and coil to fire (ie which cylinder is TDC compression and which is TDC exhaust) as in paired cylinders 1 and 4, which both are at same crank angle.

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When you say paired cylinders, do you mean they fire 1 and 4 coil simultaneously? If so that is what I meant by wasted spark, as only one of those 2 cylinders will be on the power stroke at a time. Thank you for clarifying how Porsche does this.

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No, by paired, I mean they both have the pistons at TDC at the same time,(one on TDC compression the other on TDC exhaust) that means the flywheel is at the same position for both cylinders.(2 revolutions to complete the 4 cycles) It is not a wasted spark system, coil 1 and coil 4 fire independently.

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Thank you, I appreciate you taking the time to explain it.

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Your welcome

Time for an update. Received ECU D last week and we took it over to the local Porsche dealership to be programmed (" that thing again?!" when they saw my car). No news after that until I received this email from my indy this morning with the results (as usual edited slightly for clarity): So... P0201 and slight misfires without and P030_ Misfire codes, so it seems like ECU D is either stronger than the other three or less sensitive to this issue, which I suppose is an improvement of sorts? As you can see we're back to the idea of swapping the #1 and #2 injectors to see if the fault codes move, but assuming they don't I'm wondering if the only option left to us is to replace the harness? Frustrating to say the least. On an interesting-but-probably-completely-unrelated note, remember how I mentioned we'd discovered a leaking cam sensor that was wicking oil into the harness, but we believed it was likely unrelated because oil is an insulator and we had been testing bypassing the harness injector wiring? Check out this video about oil behavior when exposed to high voltages that popped up in my Facebook news feed this morning. It's admittedly about cooking oil, but I'm wondering if the whole "oil is an insulator" idea isn't necessarily completely consistent when we're talking about the amount of voltage/current that passes through the harness to the injectors (not enough to become a conductor, certainly, but maybe enough to conduct just enough current to mess up the system?): https://www.facebook.com/SciencePagecom/videos/673048176483595/

I don't be believe control voltage to the injectors is high enough to cause that. Output of a coil...you bet. Injector voltage I would be skeptical.

Geezus !! , I thought you had already swapped the injectors and the problem did not follow the injectors??

Quotes source posts: 15801092, 15801313

Me too(!), but at this point we're looking for something on that level of unlikelihood and I'm wondering if oil in the harness is allowing coil voltage to interfere with injector signal continuity or something like that. Doesn't make much sense, but we're getting to the point where we've tried everything that makes any more sense. We swapped the #5 and #6 injectors and even replaced the #5 with a new one altogether when we were still using ECU A (which is the only one of the four DMEs that manifested symptoms with cylinder #5 rather than cylinder #1). We were planning on swapping the #1 and #2 injectors a couple of weeks ago before buying/programming ECU D but my indy ran out of time working on the rest of our lengthy to-try list and that step got skipped.

It sure seams plausible that DME A is incorrectly stating cyl 5 when it really is cyl 1 injector all along? That would explain why 3 other DME�s say cyl 1. It sounds like the injector for cylinder 1 is original, and untouched?(!) Have other checks been done to confirm which cylinder is actually misfiring? If you put DME A back in and unplug injector 1 when it�s misfiring does it log both cylinders� misfires AND injector circuit faults? (I would much rather swap the injector real fast than swap DMEs)

Quotes source post: 15802009

Yes and no... We've definitively established that the misfires are located at cylinder #5 when ECU A is installed (both through the oscilloscope testing on a previous page and earlier with a NOID light on the circuit), but that doesn't necessarily mean the problem is located in the cylinder #5 circuit. My best way of describing it is that people don't always experience the same symptoms in response to the same disease. The misfires are a symptom, or rather, they're a symptom of a symptom! The primary symptom is missing fuel injector signal pulses: the cylinder misfires because the injector is never told to put any fuel in. The disease, whatever is causing the missing fuel injector signals, is the real mystery. On ECU A that symptom manifests with cylinder #5, on ECUs B, C, and D it manifests with cylinder #1, but it remains a possibility in my mind that the disease itself might not be on either of those circuits (or for that matter on any of the injector circuits!). That's why we did a lot of the other testing detailed above, such as replacing the coils, cleaning/unplugging the MAF, etc and also why I'm speculating about such wildly improbable things as glitches as a result of oil in the wiring harness (improbable because oil is an insulator, we already know that oil's been wicked into the harness as a result of a leaking cam sensor).

Have they tried running a separate wire directly between the DME and injector #1 or 5 to bypass the engine harness?

Also, was the signal measured at the injector or the DME when they used the scope?

Quotes source posts: 15802407, 15802412

Yes, unless I'm mistaken we've fully bypassed the harness for each of those injectors at separate times. At the DME, so the missing signals are not getting sent rather than being lost along the way. Both of those facts are what leads me to wonder if "the disease" is elsewhere in the harness wiring and these misfires are simply the different DMEs manifesting the symptoms in different ways (meaning there's nothing wrong at all with those injectors or their wiring).

When the DME detects a fault in the circuit it stops triggering the injector as mentioned above. It sounds like you have confirmed that DME A stops pulsing cyl5 injector(and DME�s B-D stop pulsing cyl1 injector). This could still (and bare with me as this is reaching) be caused by DME A sensing an injector out of tolerance (actually cyl 1) but mistaking it for 5 and stopping cyl 5 injection. That is why I asked if you unplugged injector 1 with DME A causing a known circuit fault does it register cyl 1 AND 5 injector circuits? I have to believe DMEs B-D at this point...which all blatantly point to a component that you have not replaced or swapped positions of?? In all my years working on these cars I�ve almost never seen a control unit incorrectly diagnose an electrical circuit fault due to a completely separate circuit unless someone has hacked the harness wiring (previous rat damage repair or screwed/drilled into harness wires?)

Quotes source post: 15802451

I've wondered about that exact scenario (ECU A misidentifying the problem cylinder), but my indy thought it unlikely when I was picking his brain about it a couple of weeks ago. Hopefully this injector swap will tell us something!

Sorry for the delay, my indy�s been working on the car in little bursts with long gaps in-between as other cars come into the shop. Here are the latest updates: First, while talking with him the other day we realized there�d been a slight miscommunication early on in this process: the [now replaced] cam sensor that had been wicking oil into the harness was actually a cam actuator rather than a cam sensor (this likely makes zero difference whatsoever to my misfiring problem, but I wanted to correct it here just in case). We swapped the #1 and #2 fuel injectors with zero change in the behavior of the car: ECU A continues to misfire on cylinder #5 and ECU D �misfires� (injector fault codes and the noticeable slight shudder of a misfire, but no P030_ misfire codes) on cylinder #1. We also realized that there�d been a misunderstanding on my part regarding what harness wiring we had/hadn�t bypassed. Turns out we hadn�t done ANY bypassing of the wiring for the #1 injector up until this point, so we completely bypassed the injector circuit (battery�injector�DME) and retested with both ECUs A and D: still no change. Lastly, and this may be an important clue, we continued to learn more about what *exactly* triggers the P020_ fault codes. Back on the 26th I shared a message from my indy saying the three conditions that cause an injector fault code (quoted below), but it wasn�t until I spent some time with him at the shop I understood exactly what it meant on the waveform about an �induced voltage.� It's not referring to the actual fuel injector signal pulse like I originally thought: it�s referring to the tiny spike at the end of each signal pulse (a couple examples are circled in red in the upper left section, plus I approximated where the missing injector signal would be): What�s interesting is that if we had an actual injector circuit problem we�d expect there to be something different -somehow about the �test pulse� (what I�m calling the induced voltage that checks the circuit) immediately prior to any given misfire. As in: after the injector fires normally (downward box wave), the following test pulse would be somehow misshapen (different voltage/shape/etc to indicate a circuit issue), which the DME reads as a problem and thus the next injector pulse is never sent. Instead, on every waveform image we�ve taken, the test pulse prior to a missing injector signal looks completely normal in size/shape (see the bottom right image above, where I used purple to circle the test pulse and show where the missing injector signal goes). So� At this point we�ve got two theories. Either, A) We have FOUR bad DMEs. Or B) There is something going on electrically in the car, likely COMPLETELY outside of the six fuel injector circuits, that�s causing internal glitches within the four DMEs that they are each manifesting in the form of missing fuel injector signals. If the fuel injector is never signaled in the first place there wouldn�t be any, er, �rebound voltage� to form the test pulse, so the P020_ �fuel injector circuit� faults are merely symptoms of the missing injector signals rather than symptoms of what is causing the missing injector signals. Any thoughts?

I realize that my explanation above may be poorly-worded/confusing, so for the sake of clarity here's how I described it when emailing the theory to my indy:

I would start with a visual inspection of the flywheel -that is the basis of all the timing .The issues appear to be around cylinders 1 and 5 .Firing order is 162435 -Depending on which dme cylinder 1 or 5 is flaky suggests flywheel .Also is cam deviation ok ?

Quotes source posts: 15832607, 15777361, 15777428

I'd previously discounted the flywheel idea because of the way the problem moves based on the DME installed, but I decided to look back over the flywheel discussion from a couple pages ago and focused on these posts: ...particularly this comment from @jumpy chunky "Also the fact that the misfires are more pronunced when heated up, the crankshaft position sensor would have a harder time picking up a signal from bent teeth throught hot air as that is denser than cold air. " This is admittedly a reach, a LONG reach, but is it possible that there's a bent tooth related to cylinder #1 on the flywheel that would only be sensed intermittently/randomly (glitchy sensor? only slightly bent?) AND cause: -ECUs B/C/D to misfire cylinder #1 (by failing to send signals to inject fuel) regardless of whether the engine is cold/warm (correctly reading the location of the bent tooth, but not always reading it as bent because they each vary in how often they misfire) BUT THAT -ECU A would read normally on a cold engine (normal operation of all cylinders) and then misread as a cylinder #5 tooth when the engine is warm (causing cylinder #5 misfires)? That's a whole lot of overlapping weird malfunctions, so even if it happened this way once or twice I'm really struggling to imagine a circumstance where it'd reliably switch to cylinder #5 whenever ECU A is installed many times over the span of several months (you'd almost have to have a slightly bent cylinder #1 flywheel tooth AND an unreliable sensor reading it AND a failed original DME that would misinterpret which tooth the sensor is unreliably sensing), but that's why I want to run it by you experts before we consider a job as big as inspecting the flywheel. The other main idea that we're considering at the moment is a replacement of the entire engine harness based on the theory that this is an electrical/wiring glitch somewhere other than the fuel injector circuits. It's also shot in the dark without any direct evidence of bad wiring, but maybe slightly less Rube Goldberg-esque than the flywheel/sensor/DME theory? I don't know.

So new guy here,, but I read though this one,, and thought I'd toss something out,, I had a similar issue(Not on a Porsche) , the root cause was iron filings stuck to the flywheel in the notches for the crank position sensor. Result of a starter swap that had dropped some magnetized shrapnel where it would touch the sensor. I've also had a flywheel dropped, and it dented the edge of one of the grooves and it would not fire without the CPS being at minimum clearance. Oh and A bad CPS sensor can play head games with the ECU.

post 46 is another data point

You can get a good look at the flywheel teeth by removing the starter and rotating the engine by hand. It may be worth the trouble just to eliminate that as a possibility since this issue is so alluding. But as I mentioned before cylinder 1 and 4 use the same teeth, cylinder 6 and 3 use the same teeth, and cylinder 2 and 5 use the same teeth.Takes 2 revolutions to fire all 6 cylinders(order 162435), on one revolution cylinders 1-6-2 use all the teeth, on the next revolution cylinders 4-3-5 use all the teeth..By all logic, is you have a bent tooth that effects cylinder 1 then it should effect cylinder 4 just the same. But stranger things have happened, so may be worth having a look. Dr. h.c. Porschetech3

Question for Porschetech 3 -in the lsx world there is a crank shaft position sensor relearn procedure for synchronizing cam and crank .Usually used when misfires are random or a new ecm (dme ) is installed .Does pwis have a similar procedure ?

Quotes source post: 15837688

Good question. There is a learning procedure/duration for the misfire monitor. When/if the DME is reset/new the misfire monitor is less sensitive untill after the learning procedure/duration (will not show misfires as easily, but will show injector/coil electrical faults). This is done to help with "false misfires" due to rough roads/pot holes ect. effecting flywheel speeds. The DME "learns" the flywheel teeth exact profile discrepancies and cylinder assigned. The synchronizing of cam to crank is done by cam position sensors.

Quotes source post: 15837927

Thank you .Good idea on checking the teeth thru the starter hole .My thought on the flywheel was not a tooth but erratic dampening which is pure speculation .

Is it possible that the dual mass flywheel could wobble if the integral dampener is failing, resulting in erratic readings by the sensor? Yeah, I know, off the wall, but thought I'd ask.

Quotes source post: 15838149

The flywheel teeth/ sensor ring is part of the fixed primary mass, so would not wobble. The secondary mass/ clutch can wobble or be improperly dampened or even become fixed/ stuck. I have seen dual mass flywheels fail in all those sceinerios, but didn't result in injector codes, the results are vibration, knocking noise, transmission ringing sounds when lugging. I have never had it cause a misfire/ injector code and would think it would be random if it did. If any of these other symptoms are present I would certainly replace the DMF and see if it solved all problems..

I forwarded all this discussion to my indy yesterday and just heard back from him: We haven't observed any of the other issues @Porschetech3 mentioned in post #75, so I think this seems like a sensible way to test this theory. Of course, if there are issues with the scope output we'd still need to determine if it's a problem with the flywheel or the sensor, but if the signal comes out clean it shouldn't it eliminate both?

I've had CPS and TPS sensors drive me bonkers, partial thermal driven failure on either can make you pull your hair out.. One test is run the car till its hot, then when the engine starts missing, spray the CPS with cold shot to cool it and see if the miss stops. Same with the TPS and cam position sensors,, don't deluge the part, you just want to cool it a little to see if the miss is heat related. Its also sold under names like circuit chill, part freeze and others basically you can also just turn a can of "canned air" upside down so it sprays liquid to get the same effect.

Quotes source post: 15846441

This is good to know since it makes this possibility seem less "out there!" I've been thinking we should first try scoping the CPS output with ECU D installed because ECUs B/C/D all have cylinder #1 misfires even when the engine is cold (so if it's a bent tooth it should show up in the CPS waveform from the get-go), but those results are inconclusive a can of cold shot and ECU A might be helpful! Thanks! Still waiting for news: one of the things I've learned is that anytime my indy says he's going to work on something "today" he jinxes himself and something comes up that keeps him from touching the car for the better part of a week.

Your mechanic should be looking at live data when the missfire starts and see what sensor seems to be out of whack. Pulling the codes is not enough.

Took a couple of weeks because of how overloaded the shop is, but we were finally able to scope the CPS output today and compare CPS data with the missing injector signals: nada. Nothing apparently abnormal in the CPS output (although the ECU noticed that the scope was hooked up and threw codes related to the CPS as a result, but those only occurred while the scope was there) when hooked up directly to the CPS. Here's the email from the indy: So he's back to the "bad ECU" theory, which I just can't wrap my head around after throwing three replacements at it already and not even being able to return two of them because of expired return windows (plus the non-refundable programming fee). A bad original ECU + something else bad made sense as a possibility (especially when all three replacements glitched on cylinder #1 instead of #5), but not three replacement computers all with near identical malfunctions. What else could be providing bad/flaky input data to the ECU that'd cause it not to send injector signals? We've scoped the CPS and cleaned/unplugged the MAF, so replacing either of them doesn't seem likely to accomplish anything. Test the wiring to the CPS? Replace the whole engine harness as a shot-in-the-dark to eliminate wiring? Take it to Porsche?

Question -were all of the dme's loaded with new software from the dealer ?

Quotes source post: 15873518

Yes, all except the original were programmed by the local Porsche dealer.

All assumptions have been hardware -perhaps somethings amuck in the software .Porschetech 3 might have some insight on that point .I sure don't .It would be interesting to know where the indy picked up the cps signal at the connector or at the dme ?

Quotes source post: 15873549

I'd think it hard to believe, but then again we're way past "hard to believe" at this point, so maybe? @Porschetech3 , ever heard of a dealer having issues with faulty software loads/programming? Anyone else? Should I pick up ECU C and send it down to Specialized ECU in Florida like I did the first one and see what their diagnostics comes up with? He was hooked up to the CPS to keep the wiring from being a factor in the test.

Just thinking outside the box for a min, but has the alternator rectifier been checked? It has 6 diodes ,3pos and 3 neg, if a doide is blown it will cause an unusual ripple in th3 whole electrical system and can effect sensitive electronics. Just a long shot, but should be ruled out.

Quotes source post: 15873560

The only issues I have ever seen regarding DME software/programming has been wrong programming codes entered, which results in bricked DME, wrong selection of software (ie wrong country, transmission, engine type) resulting in erroneous codes, interruption of power supply, which results in bricked DME.

You�ve double and triple checked the grounds for the DME and injector harness? It sure sounds like your issue is worse under vibration and heat (engine running), but everything checks out good on the bench..... that screams ground interrupt to me or signal interrupted.

If it were me I would start with the basics -post 46 is a good starting point .Visually inspect the flywheel and also the camshaft timing .The scope test proves the teeth are there and the cps is working .Harmonics per post 46 could be a factor .

Quotes source posts: 15873576, 15873669

Good idea. We've "checked" the alternator, but I don't know if we've specifically checked the rectifier for it. Thanks! Off the top of your head, do you happen to know of any diagnostic equipment the dealer might have that an indy shop wouldn't that might be useful in this situation? Aside from a fresh set of eyes, it's hard to justify the hourly rate of taking it to them if they're just going to do all the same stuff we have (especially considering how far in the hole I am already on this car!). The only thing I've thought of is that they'd be able to ask Germany "what inputs are used by the DME to determine when to send injector signals?" to try to narrow down the list of possibilities.

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We've even augmented the DME ground with a second wire! We've spent the last few months chasing our tails on the injector harness and injectors, but I think those scope tests from a few pages ago (recorded on the road, not bench tests) showed pretty conclusively that the injector signals aren't getting lost in the wiring or disobeyed by the injector: they're simply not being generated by the DME in the first place! Whatever the problem is it seems to be on the input side of the DME and the "injector circuit fault" codes are merely a symptom of the missing signals rather than being related to the cause.

Quotes source posts: 15874680, 15779943

Just to save everyone some scrolling, here's the post he's referring to: Hmmm, I must be missing something here; I'm having trouble following your train of thought on this one @dcdrechsel ... The theory behind testing the CPS, at least as I understood it, was something like "minor damage to the flywheel might cause intermittent glitches/distortions in the signal from the CPS (meaning the damaged tooth is sometimes seen by the sensor and sometimes not), causing the DME to intermittently miss its cue that it's time to signal the fuel injector." No fuel injector signal=>misfire and no "rebound voltage" on the back side of the injector signal (generating the "injector circuit" code because the DME notices the voltage to test the circuit is absent). If the test shows "the teeth are there and the CPS is working" as you say, and if we were able to time-correlate missing injector pulses with "normal" CPS signals, how could harmonics or other flywheel issues interfere with the DME sending/failing to send injector signals? How would those issues be communicated to the DME if not through the CPS?

I am by no means an expert but If the flywheel is oscillating - the dme predictable pattern is disturbed which could cause strange faults .I would ask Jake for his thoughts …………...Further I believe the IMS was upgraded before your purchase which makes that work suspect .

Quotes source post: 15874979

Your Indy seems to be very competent and thorough, and is using an oscilloscope which is invaluable in these situations. I don't know if he has Piwis, but it gives a lot more information and actual values than Durametric or other equipment. Most dealers also have a "breakout box" that goes between the DME and wiring harness and allows quick and easy testing of resistance,voltage and scope tests for anything coming or going from the DME. Dealers also have access to the "Porsche Hotline" of engineers in the Atlanta Center that love challenges like this, and have a data base that has seen everything. All problems like this end up at a dealership and most have contacted the "hotline" and solutions are entered into the data base. As a last ditch solution there are " Regional Service Field Engineers" that can get involved and instruct the Technicians on testing and troubleshooting, and sometimes will make a special visit to the dealership in person (or if there is no rush, they come around every so often anyway to check on things). Before I retired Jimmy Hays was our Regional guy, very sharp, I don't know if he covered PA or if he is even still with Porsche, but all of them are good. The "fresh set of eyes" comment might be what is needed. Many times these kinds of problems turn out to be something really simple, that is causing strange symptoms/codes, and a fresh eye or fresh approach can spot it quickly/easily. Like I said earlier, at this point I would pull the starter to get a good look at the trigger teeth of the flywheel, and fashion an indicator wire and rotate the flywheel by hand to check for irregularities/damage of the flywheel trigger teeth. I know the scope pattern looked good, but at this point nothing should be assumed.

If you reset the DME, does the error code pop up and the engine misfires immediately or the engine runs fine for sometime but then turned into this failure mode?

Quotes source post: 15875419

It's good to know they have those resources available. When I originally ran your starter idea by my indy he agreed it'd be a lot easier than pulling out the whole flywheel but then added that pulling the starter wasn't all that quick/easy either (which is when he came up with the idea of scoping the CPS). Aside from your idea of checking the alternator rectifier diodes, my current leading two options are having the indy pull the starter as you said or just giving up now and taking it to Porsche along with the now VERY long list of things we've tried and learned so we don't waste time/money recovering the same ground. Either way it'll be expensive. :/

Quotes source post: 15875574

Right away. Or rather: identical behavior to an un-reset DME, which varies depending on which one is installed (ECU A needs to warm up a bit and then misfires on #5, ECUs B-D start misfiring on #1 before you even get it out of the parking lot).

One more question. Has the mechanic ever scoped both the ignition coil signal and injector signal (of the misfiring cylinder) at the same time? I want to know when an injector pulse is missing whether the ignition coil pulse is also missing. If so, it seems the DME is trying to shut down that specific cylinder. If not, it is even more weird.

Have you tried measuring the supply voltage to the DME ECU? Also the 12V supply for all the injectors and coils?

Quotes source posts: 15875864, 15877861

That would have been a good think to scope, but considering how many of the misfires are single-misses it seems like it'd be odd to try to shut down a cylinder for a single rotation and start it again on the next one. ECUs B-D do eventually shut down the #1 cylinder altogether, but only after a number of intermittent misfires. I don't think ECU A ever went into a full-shutdown mode on #5 in our testing. I don't have it specifically in my notes, but I'm pretty sure we've measured those for at least the ECU and the injectors (not as confident about the coils).

So... I caved in today and decided to take the car over to the local Porsche dealer to have them do diagnostics on it. Aside from the couple of out-of-the-box suggestions that have been offered on here over the last few days, we're just totally out of ideas at this point aside from yet another ECU. Before I took it over there I wrote up a list of everything we've done and learned so far to get them up to speed without having to cover the same ground or chase some of the same dead-ends like the injector circuits (it ended up being 4 pages long!). I'm still pretty-confident that the problem is external to the DME (some sort of ripple or bad input that's confusing/glitching otherwise-fine computers), so my single biggest concern is that they're going to come back and say "it needs a new ECU" before diving deeply-enough into the problem to be confident of that answer (a $3000 not-returnable/refundable gamble if we try it and the problem persists). While talking with the service manager I told him about how Specialized ECU had given ECU A a clean bill of health and he said "they do good work: I've sent stuff to them before," so hopefully that conversation will help persuade them to look deeper during their testing. They won't get to the car until later next week, so stay tuned and I'll let you know as soon as I hear anything!

This is such a great technical thread. It sucks the fix has not been found but for us tech heads its about the ride. Hope the trip to the dealer works out.

Quotes source post: 15878368

My thinking is this. Perhaps not so much about DME trying to shut it down but rather the DME cannot find the right cam position to trigger it. IF the coil signal is missed together with the injector signal, at least the DME is consistent, which points to NOT a DME problem. It's something that's causing the DME to not fire the cylinder. Since the offending cylinders are 1 and 5 and they are next to each other in the firing order, I wonder if there's some irregularity with the cam reluctor(s) such that the DME has to compensate/learn such thus cannot fire all cylinders but can only fire 5 out of the 6. Some DME gave up on cyl #1 and some on cyl #5, due to the way they learn the irregularity. This theory is totally out there but your case is totally out there anyway. Another possibility is is it possible the ping sensors play a role?

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Any update on this? This thread went so deep it would a shame to not have a conclusion on it !!

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Thanks for asking! I'm living in limbo: no news one way or the other. It's now been a full month since I dropped it off at the dealership and was told it'd be a week before they got to it. When I spoke with them about two weeks ago they told me that they'd gotten completely slammed with work right after I dropped the car off, so they'd barely spent any time on it at that point (the person I spoke with thought she might have heard the tech had "an idea," but I never heard anything back about that so I'm assuming it didn't pan out). I haven't heard a peep from them since then, so given what they said I think it's reasonable to suspect they still haven't spent much time on it. It's not fun to be so out of the loop, but I've been trying to not bug them because I'd rather they go slow and get it right than rush an answer to get me off their back and get it wrong. I'm planning to check in with them Tuesday or Wednesday if I haven't heard anything.

Mark my word when this is all said and done I am going to figure how how I - and I imagine many more of us - can pool together to send you copious amounts of beer. That is the only thing I can contribute, but my eyes are glued to this thread. Fingers crossed for you, Shawn.

If I dropped my car off at a Porsche dealer and they didn't work on it WHEN they said they would I'd be in the service managers office. It isn't like they will do you any favors, your paying for the work, what makes your car less important than any other.. ??

No fix or technical news, but here�s an update with a major kindness and a plot twist: First, the kindness: As of last week my indy still had not billed me for the bulk of the work he�s done on the car (likely because he�s busy with other projects and because there�s been expecting to see the car again). I felt bad that his cash flow was being impacted by these delays with the dealer, so I asked him to put together a bill. He�d honestly lost track of how much time he spent on it over the course of the spring, but there�s absolutely no question that he was very generous in underestimating his time. That�s not to say the bill was small(!), but if he�d accurately charged me for the full time he�d spent it would have been much larger! He�s a great guy and I wouldn�t hesitate to recommend his shop to anyone in the area: Foster�s Automotive of Mechanicsburg, PA. I know it might seem a little odd to finally name him after all this time and without having a fix behind us, but it wouldn�t seem fair to name the dealership in this next bit without naming the indy who�s done so much to try to take care of me. Second, a plot twist with the dealership: Back in May when I spoke with the service manager about bringing in the car he told me that diagnostics would run me �about $500� (which comes out to about 3-4 hours at their shop rate). I agreed, even assumed it would probably be a few hundred more, and brought the car over along with four pages of documentation of everything we�ve done/tried/replaced. On Friday I emailed him a friendly nudge about my car and learned that they have spent the last month and a half significantly exceeding that 3-4 hours to the tune of 15 hours and counting on diagnostics in-between working on other cars, all without keeping me in the loop or asking me to approve that amount of time. No word on what they�ve spent that time doing either. Confused and concerned, I sent him an email asking to hold off on any further work until we could sort this out, but then� !!!! I still don�t know what they�ve spent that time doing, although I�m planning to meet with them on Wednesday to find out, but that�s not the point of this update: Faulkner Porsche is going above and beyond to try to help me. It�s clearly a special case rather than precedence for everyone else, but I never imagined I�d be able to say anything like that about a dealership and I think it�s deserving of some recognition here regardless of if the work proves fruitful or not. It�s honestly an answer to prayer! (Still praying they�ll find the core problem itself!) So, again, I�m hoping to learn more tomorrow and it�ll probably take me a day or three to update the rest of you because of my work schedule, but I couldn�t wait until then to share this with all of you.

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Thanks for the update and hope they have some solid clues .

If everyone is so generous then why are they charging you when they can't figure out what is wrong with the car?

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Wow! That's great! It's hard to find shops that are willing to go the extra mile for the customer these days! I hope that your issues gets resolved soon! Mike

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^^^When you go to the hospital and the doctors can't figure out what's wrong with you, or they misdiagnose you, do you still have to pay the bill? Of course you do! Unfortunately, this is just the way it works. Back to the problem: I notice you've got a C4 - have any of the mechanics checked out the "Venturi Tubes" in the fuel tank? A problem with these just had Flat 6 Innovations tearing their hair out after installing my newly rebuilt engine...just a thought. Seems a hairline fracture in one of these tubes had the engine going lean at higher rpm's when there was a high demand for fuel. Seeing as just about everything else in your fuel and ignition system has been checked/replaced, it might be worth a look see...

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I live in Canada, I don't have to pay for it. But all seriousness, having an illness is not the same as working on the car. If your furnace breaks and the repairman doesn't know how to fix it, do you pay for it?

Quotes source post: 15981376

Uhhhh, he doesn't say "sorry, I don't know how to fix it" (unless he's a really bad business person - in which case he probably won't be the one working on your furnace because he'll already be out of business...). He say's "Oh, it's just a dirty nozzle, but the furnace needs a good cleaning too"... You get charged for a cleaning, a new nozzle (including a hefty markup) and the labor to install it. If the furnace runs, great! If not, he say's "yeah, it needed the nozzle and the cleaning regardless, but now I realized it also needs a new ignition module, and the motor might be bad"...""it shouldn't be more than 3 or 4 hundred $"... Most people have no clue how to work on their furnace, so they say "oh geezzzzz... Uh, ok"...

Quotes source post: 15981376

We're taxed to hell here, we sure do pay for it.

I went through something similar - a code, followed by great difficulty and improper diagnoses to actually fix it. At one point, wiring was suspect, and the DME was suspect. I had the DME tested by ECU Doctors (they were awesome by the way, highly recommended). The ECU was fine. It ended up being exactly what the code suggested - a failed electrical part. I wouldn�t be surprised if the fuel injector itself is bad, or a crank position sensor, or coils, etc. You might wonder how or why a failed part can influence another part, but like I said, don�t be surprised.

I�ll get this out of the way first: no technical revelations out of my meeting with the dealership. I went over there yesterday afternoon and spent some time talking with J, the service manager, and H, the Gold-level technician who�s been working on my car. Both have been with the dealership about fifteen years and struck me as very knowledgeable and competent guys. They told me they�ve never been able to not fix a car during that time (plenty that the owners weren�t willing to fix, but never one they were unable to fix) and they�ve never seen a car as difficult to diagnose as mine. Just to be clear: they haven�t given up, they were just commenting on how extraordinary my case is. I was expecting to spend most of our time listening to what they�ve been doing and asking questions, but the bulk of the time was actually them asking me questions to learn more about the history of the car, expand upon the documentation I gave them of what we�ve tried, and have H and I bounce ideas off of each other. I was impressed at how open they were to any ideas I or the forum might be able to offer and there was no sense whatsoever of the stereotypical dealership arrogance. I don�t think it�d be unfair to say it seemed like they want to find an answer because not having one is driving them crazy too! It turns out they�ve spent most of their time on the car re-tracing the steps of my indy. Not out of disrespect or distrust: just a matter of them wanting to see it for themselves in case there might be clues he missed. I expect some of you might have mixed feelings about that approach, but sticking with the original diagnostic fee buys them a LOT of latitude in my mind and I�m grateful for the thoroughness. Their findings have matched his thus far and I was able to help put some of that information in context, particularly which parts of the harness we�ve bypassed and this big-picture theory I�ve been mulling on: It�s an oversimplification, but� the ECU inputs sensor data+power and then outputs sparks+fuel. IF the problem moves with different computers, it can�t be located on the output side of a particular cylinder (despite the codes pointing that direction), and IF any one of the four computers is good (statistically likely, especially considering the Specialized ECU clean bill of health for ECU A), THEN the problem must be something on the input side that�s confusing the computers and causing missed fuel signals. H thought that seemed reasonable, but he wants to do one more circuit test by bypassing the harness for the #5 ignition coil just to be sure (a bypass my indy never did because the problem moved and the codes weren�t ignition related). After that, the next step is the one I was personally hoping they�d have started with back in June: hooking the car up to the �pin-out box,� which is a diagnostic computer that can eavesdrop on all the signals going into and out of the ECU at once. If there�s a bad sensor somewhere or bad wiring from a sensor, it should show up in that data. This is the step I�m most hopeful will lead to usable information and I�m expecting to hear back from them once they�ve tried it. A few other miscellaneous notes: -I asked H what inputs the ECU uses to determine when to send fuel signals. To the best of his knowledge that function mainly relies on the crank position sensor and the cam sensor. A problem in any of the other sensors should cause problems with multiple cylinders rather than just missed fuel signals on a particular one. -H noted that when he was test driving the car he noticed a very faint possible rodent or rodent dropping odor. The car was a nice-weather car in rural Montana for several years, so it�s definitely a prime target for such a problem, but we�ve never found any direct evidence of it happening like droppings or chewed wires (I�ve personally never noticed that smell, but that�s not to say it isn�t there). Rodent damage could certainly be a factor in my misfire problem but we would have expected to find some evidence of it by now. -H said that he�s noticed a puff of white smoke when first starting the car after it�s been sitting for a week or two. I�ve had the AOS on my �to-do if this misfire ever gets resolved� list as a preventative measure anyway, but I�m thinking it�s probably more a result of the oil being the near the max-fill line (not halfway like it should be) and the car sitting than a sign of impending AOS failure.

Quotes source posts: 15978799, 15981442

Because time is money: any time they spend trying to diagnose my car is time that could be spent on billable hours working on someone else's car. It's the same as a lawyer charging for the entire time they spend working on a case instead of just the time they spend in trial arguing it: you're paying for their time working on the issue even if there's a 90/10 split between time spent on preparation/argument (analogous to diagnosis/repair). Unfortunately in my case the codes have been demonstrated to all be symptoms of another non-coded issue, so chasing them has proven to be a significant misdirection. Something is causing the computer to not generate fuel signals in the first place: no fuel signal means there's no voltage to test the integrity of the injector circuit (P20# injector circuit code) and no fuel means nothing in the cylinder to ignite (P30# misfire code). Glad your code proved more helpful and that your issue was resolved!

Quotes source post: 15981287

That was a fascinating discussion, wasn't it? I never, EVER would have guessed or found something like that and I'm amazed FSI was able to find it without taking a lot more time than they did. I'll have to ponder it a little more if the pin-out computer doesn't give us anything useful: my first instinct would be that it doesn't seem likely because a couple of the computers still experience misfires at idle and the problem is always limited to one cylinder, but maybe I'm wrong on that?

Sounds like you got some great people at the dealership. This story gives me hope. It actually sounds like how I troubleshoot and how I treat people (most of the time). LOL

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Sorry if I missed this, but did they check the resistance of each injector and coil? Or measure draw when activated? I had a situation where internal shorting was causing the DME to appear to not activate or appear to be a failed ground because the DME has transistors that simulate on/off with the transistors. Yet manual activation on the shorted part still showed that part was working. Do the injectors work like that? Could an injector somewhere else cause another injector not to work? Are there any shared connections among the injectors (like shared grounds)?

My car gave a little puff of smoke at start up a few months before my AOS failed FWIW. Daily driver! Good luck.

Did you share Ashai's hypothesis with them ?I don't know the diagnostic capabilities they have with the pinout box but it could be something that they look for .

Quotes source post: 15982855

Resistance and draw of all six injectors were checked, along with the continuity of the wiring to the "problem" injectors #1 and #5 (including doing a complete bypass of the harness for at least #5 injector and I think #1 as well). We also hooked up an oscilloscope directly to the DME and observed no output signal being generated (it wasn't being lost in the wires and wasn't a case of a failed injector not responding to a signal). The injectors do share a ground, but our bypass testing included bypassing that and grounding the problem injector directly. More importantly, when ECU A (the one with cylinder #5 problems) is installed cylinder #1 runs flawlessly at all loads and when ECUs B/C/D are installed (which have cylinder #1 problems) are installed cylinder #5 runs flawlessly at all loads. If it helps, especially for anyone joining the thread who hasn't had a chance to read it through yet, here's a copy of the document I gave the dealer providing a brief history of what we've done/learned thus far:

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My understanding is that the puff is only occurring at start when the car has been sitting for a few days+. AOS is the top priority after the misfire fix and it'll definitely happen before I daily drive it. Definitely has me a little nervous to put it off even that long but it's also tough to justify doing that sort of work when the car is in the condition it's in (not really driveable and no guarantee they'll be able to find the problem).

Quotes source post: 15982878

Good question. I haven't, so thanks for reminding me of that post! I'll have to pass it along to them. Hopefully it's something they'd be able to see in the pinout data.

I'm glad your indy and the Porsche dealership are being nice to you . They sympathize with you and know this unusual problem is not your fault. It also shows good on your character also, most won't be so nice with someone who is a jerk. I really don't blame the dealership for going back over some of the same things your Indy has already done, I would have too. Just a thought that could explain why DME A shows a fault on injector 5 while the others show a fault on injector 1. There is a good possibility that the software is different between DME A and the others. The software version can be displayed in PIWIS and should be checked by the dealership just for information sake. All the software versions will be legal for EPA in all states in the US, but there can be a lot of differences to correct or improve some functions/strategies/calibrations. DME A could have an older software version. I hope you get this issue corrected soon, I am very interested in what the solution is. As far as any suggestions or idea's, all I can say is like I have already said before, I would do a visual inspection on the flywheel teeth before I went on to more "out-of-the-box" theory's..

Possible good news? Just got a call from J (the service manager). He said they are now highly confident that it�s a wiring issue. H has gone over the mechanicals of the car in great detail (even correcting the slightly-off installation of the coil spacers from when they were replaced) without finding anything. Then, when they finally hooked the car up to the pin-out box, it stopped misfiring altogether! Apparently, I was mistaken about how the pin-out box works. I was under the impression it sandwiched between the connectors of the ECU and the connectors from the harness, but from what J said it sounds more like �the anaconda� as they call it outright bypasses the entire harness at once ( @Porschetech3 , maybe you can clarify this?)! Therefore, if the misfire stops when the harness is bypassed, it�s all down to a matter of finding the bad wire. H is now methodically testing every wire in the harness and they�re hopeful that he�ll be able to find the bad one yet this week. It still wouldn't explain exactly why the misfire moves between cylinders when the computer is replaced, but if the bad wire is on the input side it'd fit my theory of bad input data confusing the ECUs and each one responding to the glitch differently. J also asked me to agree to a higher-than-planned diagnostic fee after all, $1500 instead of the original $500 (10 hours vs 3.5), because H has now spent around 40 hours working on the car. I agreed because it�s not an unreasonable thing to ask and IF we�re right that it�s a bad wire the �fix� itself shouldn�t be expensive at all (they do deserve to get paid after all!). If/when the bad wire is identified I�m going to ask them to test run the car with one of the more misfire-prone computers (C or D) as a way of double checking that we�re finally sorted before they put the interior back together. I think the original computer (ECU A) is the best of the lot, so that�s what I�m planning on having in the car long term. And then maybe retitle the thread �The $10,000 Wire�? We�ll see, I�m trying not to get my hopes up too much.

Fingers crossed, brother, this one has been a nail biter. And I was serious about the beers

The "pin-out" box does not by-pass any of the original wiring harness, it adds more harness to it, with the provisional box to facilitate tapping into all inputs and outputs for diagnosis. Installing the pin-out box should not correct anything unless it is a connection problem. But with as much disconnecting and reconnecting as this car had had with all the DME swaps, a connection problem should have already surfaced by either getting better or worse. I don't want to rain on your parade, but I'm very skeptical at this point. I'm very surprised he has spent 40 hours at this point and is just now hooking up the pin-out box. I hope that at least within that 40 hours he at least verified the physical condition of the flywheel teeth.. I'm rooting for you...

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As always your honest input is appreciated and I don't think your skepticism is ill-founded! Aside from the wiring being very high on my suspect list for a long time (confirmation bias, anyone?), the only element that is making me hopeful about this report was the news that the misfire went away while the pin-out box was connected. That wouldn't happen if it was the flywheel unless they simply didn't test it properly while the box was connected. I'll need to ask them specifically about the flywheel when we talk (even if it proves to be a wire I'm hoping to get a much more thorough understanding of what they looked at/tried for general knowledge about the condition of my car). I'm honestly more confused than ever at exactly how the pin-out box connects, but from the way J described it it sounded like it augments the harness somehow (he even used the word "bypass," although I don't recall exactly how he phrased it). Maybe if there's a bad wire the "more harness" wiring of the pin-out provided a clear signal path around the problem spot?

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The only thing I can think of that would make any since (besides a connection issue) is that there was an RF ( radio frequency) which is always produced by wave forms or coil osolations, that had gotten magnified by the oil saturated wiring inside the harness, and is disturbing/confusing/contaminating the signals to the DME. And lengthening the harness with good/grounded/insulated length of harness could have reduced the RF interference. I know this sounds really out in left field, even "outer limits" zone, but the most difficult problems I have ever dealt with were caused by RF interference. But I rarely mention that because they are so rare, that people think your a quack for thinking of it.. Also they need to check the software versions of your DME's. It would be great to know if DME A has a different software from the others.Could explain some things.

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You're not wrong: that's so bonkers it does sound like a quack theory! My head has been hurting just from trying to process through it! But, at the same time.... we're definitely going to be in that sort of territory if the harness testing doesn't pan out! I'm going to wait and see what they say in a few days since I don't want to pester them, but is it a correct understanding that if you're right the only solution would be a whole new harness?

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Well, IF RF interference from oil saturated wiring is causing the problem, the best and proper repair would be to replace the harness. I would suppose you can try to by-pass the wiring (like you did with the injector wiring) for the CPS , or cam position wiring, if you knew for sure which wiring the interference was coming into the DME on. But RF electromagnet interference is almost impossible to detect, an oscilloscope a lot of times won't detect it because it is in a part of the RF spectrum the the scope doesn't see. A Spectrum Analyzer would be more useful at detecting RF electromagnetic interference. Modern automobiles produce lots of RF electromagnetic interference, all electric/electronic devices do. Every injector, coil, solenoid, relay, ect produce RF EMI and can combine to produce waveforms very similar to the CPS waveform., but good designs have filters in place to filter out the EMI noise , but if the EMI noise is magnified or amplified, it can be more than the filter can handle and gets through. Like I said, this is "outer limits zone" and should be a saved for after "all else fails" before going down this road..

Cue the Twilight Zone theme music... (Rod Serling's voice over proceeds): A exasperated man stares at his Porsche 911. It sits in the shop as technicians prod and probe it, attempting to diagnose the source of electromagnetic interference that's causing the engine to misfire... The man dons a tin foil hat and checks the balance of his bank account, all the while wondering if he's wandered down a rabbit hole - into - The Twilight Zone...

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lol..Exactly !! Technicians hate getting pulled into the rabbit hole too. But they do sometimes by not wanting to be accused of "throwing parts at it", while sometimes it is the best/most economic way to fix the problem. Maybe the best solution to this is to 1, physically inspect the flywheel teeth ( which I think still hasn't been done).. 2 if the flywheel is ok, throw a good used harness in it.. Seems a better use of time and money than pondering on it for 40 hrs. to no definitive answer. Then if the harness fixes it, can be said "it was a simple wiring issue" and not mention the " Twilight Zone" explanation...lol

Can't they just completely bypass the entire wiring harness between the suspected injector/s and coil and the DME? This way they can eliminate any possibility of a harness issue.

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The offending injector has already had the wiring by-passed. From the oscilloscope reading, the DME is not sending the command for injector pulse when the misfire occurs.

How much money between all the shops combined do you have in chasing down this issue?

This reminds me of a issue a friend had. He's a BMW motorcycle mechanic. Bike comes in with similar type of issues as OP's car, my friend checks every connection in the harnes for intermittent short or open -- no luck -- checked mechanicals, replaced coils and plugs checked sensors...the whole 9 yards. Then he puts in call to BMW engineers and they ask for data and dont believe him, even tried another DME -- still no luck and the 6 weeks they had the bike is really pissing off the owner. They then send him a pin-out board and skype him while he is checking the bike out and the whole bike flashes off/on. The engineers were perplexed so they suggested he replace the wiring harness and send the old harness to them. He does as suggested and bike works perfectly now. Turns out the engineers found two wires that had rubbed their insulation off against each other. For the most part the wire part was not touching full time but close enough and under the right conditions causing shorts across each other and they didn't show continuity across each other when tested... These beasts can really beat you down sometimes. Hang in there.

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The entire harness was bypassed right from the DME to the injector and the coil harness for the same cylinder? The DME should be shutting down the injector if it thinks the spark plug isn't firing. This happens to save the cylinder from the oil getting washed down by fuel and destroyed.

Quotes source post: 16026801

Other way around: the DME is intermittently not sending fuel. We aren't sure, but we believe sparks are still being sent to the fuel-less cylinder. It's like the DME has gotten absent minded: it "forgets" to send fuel and complains when there's no rebound voltage at the end of the fuel pulse (P020_ codes), but even then it still seems completely unaware that there was no fuel signal in the first place (meaning the codes are symptoms rather than signs that could help lead us to the cause). If you want more info without reading this entire lengthy thread, I'd suggest looking at the summary document I gave the dealer that's attached to post #125 .

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There's been some other minor work along the way (tire mounting/balancing, replacing a sensor related to the headlight leveling system, a few other minor items) that's included in this number, but all told I'm at $9k so far on an $18k car. Yeah, I'm thinking more and more that unless H miraculously finds just such a wire in situ there's a high chance that a harness replacement is in my future. I don't think new harnesses are available, so there's the gamble that comes from used parts, but it'd also be the only remedy if there's merit to the oil+RF theory.

Porsche should still be selling new harnesses. The car is not that old and they made many of them and the spare parts to go with them so new OE parts should be still available.

I bought a harness that was like new from a dismantler for a fair price. Rodents had eaten the original.

Got a potentially very exciting email today: I�ll keep you guys updated as I learn more about exactly what he did! He went on to say that he was expecting to get the car put back together later today or tomorrow, but I probably won�t be picking it up that soon because I want to do the AOS before I put any real miles on it ( @808Bill has me spooked and I�m currently waiting for them to get back to me with a cost estimate for that job). I�m excited about this news, but this has been a long enough journey that I don�t think I�ll fully believe it�s fixed until I�ve got a few hours worth of misfire-free driving behind me. Stay tuned for the technical details when I get them!

Sounds like good news!

Just to make sure the misfire is fixed, drive it for at least a few days before getting the AOS replaced.

That sounds like very positive news to me !!!!

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Quotes source post: 16034389

Awesome news! Look what I just discovered, my new AOS has fractured...Coolant leaked after an hour drive the other day. Genuine Porsche!

Just got word on what the tech did! I�m still parsing through all of it, but the tl/dr seems to be that the core of the problem was related to the ignition coil ground wires for cylinders 1, 2, and 3. H sent me a 2+ page document listing bullet points of most of what he did (he admitted there was a lot that he�d forgotten to write down in the many hours he�s spent on the car) and in mostly chronological order. I�m going to copy the whole list here, including a number of notes related to the general condition of the car. I�ll change the color of the ones unrelated to the misfire to green so they�re easier to skim, add my comments in red , and bold the two most important notes: The successful 3x 10 mile and single 30 mile tests seem really, really promising to me! The car should be ready to pick up later today (Tuesday), but I�m planning on just leaving it there until the AOS is done. My life has historically been defined by irony, so I don�t want to touch it when it�d be the pinnacle of irony for this crazy problem to finally get fixed and then have the engine killed immediately afterward by something known and avoidable (considering the earlier report that the car sometimes smoked immediately after startup, knowing the oil is currently at the max fill line, and @808Bill 's experience). Many, many, many thanks to all of you who have weighed in over the course of this journey! ~9 months and ~$9000k later (not counting near-future work like AOS), I may finally be close to enjoying this amazing machine!

[Separate post for the sake of delineating subjects and preventing crazy-long quote sections:] As far as the AOS, they told me to expect it to run about $1000 to replace ($200 in parts, rest labor) and it�d be about another week and a half before they could schedule it. I�m waiting to hear back if this number means they�d do it as a full engine-out or follow the procedure I�ve heard of here on RL that only requires dropping the engine a few inches. If it�s a full engine-out, I�m trying to put together the list of �while you�re in there� items I should have them do at the same time and I�d greatly appreciate your feedback: AOS Coolant expansion tank (existing one is a little yellow, might as well just get it done) Motor mounts (pretty sure they�re original and might as well do OEM since it�ll be a DD?) Oil pressure sensor? (see H�s note about a possible bad sensor in the post above) Low Temp Thermostat? (Water pump and thermostat were replaced at 88k miles in 2015, but I think they just used an ordinary OEM thermostat. Is this something that can be replaced without further work on the coolant system?) Chain guides/tensioners? And, unrelated to engine-out: Drain a few ounces of oil to get it down toward the middle of the range (currently at max fill line) Have him search for possible cabin water-entry points? I�m planning on doing the spin-on oil filter/magnetic plug/etc with the next oil change in a few months and I�ve got a separate �to do� list I�ve been working on for the next clutch job (a year or two out?), but is there anything else I should consider doing with the AOS?

Quotes source post: 16035401

After everything you've been through!!! At least you found it quickly!

Just removing your oil filter will be enough (oil drain) and go ahead and install the spin on.

It looks like the "Twilight Zone" explanation applies to this case. The problem was found on the coil ground for bank1, but no codes were ever recorded for coil faults. And the misfire and injector codes for cyl 5 have nothing to do with the bank 1 (cyl 1-2-3) coil grounds. Loose or corroded grounds will cause a big increase in RF EMI. That's why I mentioned checking and cleaning all grounds in post #14. Your Tech (H) did it the right way (although expensive). Throwing a harness on it would have cured the problem and the loose ground would have been found in the process, but if it had not fixed the problem, the tech would have looked bad and you would have been angry spending money for nothing.. Glad you got it fixed, was a hell of a ride !!!

I'm happy they found it! I've been watching this thread closely, and I just want to repost what my single post (#25) states: That is very odd indeed. Based purely on what you have written, it sure seems like an electrical problem, and if I had to guess, something with a bad electrical connection, which could be a ground, a high resistance connection outside of the ground, or maybe even a rodent that ate part of your wiring harness . Sorry I can't be much more help, but I sure don't think you have three bad ECU's. It sounds like you have three good ones. Too bad I didn't help, pull out the wiring diagrams and actually find the ground points for the harness and make you check them! My brother told me a long time ago, the issue is usually at a connection. Hope it's fixed for good!

Glad they found the problem .I would not ignore the oil leak -the new rms seals properly installed are pretty reliable .If I interpreted the ground wire fault as partially poor mechanics might be wise to dig a little deeper on the oil leak .

Glad the problem was found and the issue finally resolved. Man, what a ride! Mike

We should start a "Go Fund Me" account for you...I'd do what I can to help!

Quotes source posts: 16035560, 16035642, 16035744

Yeah, that EMI theory makes sense and I mentioned it in my email to the tech this morning. IF this problem or anything electrical-related were to somehow resurface I think a whole new harness would be step #1 just to totally eliminate the old wiring/oil saturation issue altogether. Any thoughts on the maintenance issues/ideas going forward? Is the new-ish dripping RMS something that should concern me more than it is? You're both right: I was certainly under the impression that more of the grounds had been checked by the indy than apparently had. He's a good guy, so even if he didn't think to check the opposite bank's coil grounds as a distinct step I'm surprised he didn't catch it when we replaced the coils themselves on that side. Hmmm... maybe you're right. I'm definitely asking the tech to try to figure out where the other leaks are coming from. As for the RMS, I'm definitely not a fan of ignoring things, but at the same time I'm trying to slow the bank account hemorrhage and most of the advice I've seen seems to indicate it's not a big deal as long as you keep an eye on your oil levels. I could be wrong about that, so hopefully some more people will chime in!

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Wow Bill, I'm floored. I'd be lying if I said that the idea hadn't crossed my idle mind a time or three over the months, but then I'd always think of all the threads about much-worse situations (your AOS-blown engine, all the people with bore scoring, etc) and conclude that if anyone ought to get help it's the regulars like you who contribute so much and then have those "time to call Jake"-level problems! I'm not a wealthy guy and I certainly don't have the kind of ego that'd cause me to refuse help, but at the same time I feel like this is the kind of risk we all take in buying these amazing machines. Isn't it the other way around? I owe all of you beers for all the brainstorming and moral support you've given me!

WOOT! Hell yeah it's beer-o'clock. I'm going to PM you.

Sweet Jesus, I hope I'm not on this track. Just had 80K maintenance done on my 2009 C4S which was misfiring intermittently prior to going in the shop.Indy called this evening to say work has been completed but new plugs and coils did not fix misfire. Still misfiring cold and when warm. They will hook up PIWIS and drive it tomorrow, stay tuned

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Find someone that knows what they are doing. These guys are just throwing parts at it and making you pay.

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Shawn's motor grenade shortly after all this...I hope your indy knows what they are doing!

yeah, they just called and said I need to authorize another 4 hours for further diagnostics at $140/ hr. Cylinders 1 and 3 showing misfire, cylinder 2 showing fuel injector fault upper limit exceeded , faults for O2 sensors both banks. Now doing PIWIS drive around diagnostics versus just pulling codes. Next up, visual inspection of electrical connections in engine bay. Followed by smoke test looking for vacuum leak and if negative mass air flow sensor will be under suspicion. Prayers welcome, stay tuned.

I went through many hours and authorizations on my last repair. It�s actually not a bad sign, if they are intent on finding the actual issue, rather than guessing.

Quotes source posts: 16186207, 16187309

So so sorry to hear this!!! I never had O2 codes, but those sound vaguely familiar as possibly pointing to the MAF based on what I recall from the research I did during my misfire ordeal. Regardless, I can't overemphasize thoroughness when checking the electrical connectors and engine grounds: the bad grounds at the source of my trouble were clear on the other side of the engine from where the codes were pointing! If it's not either of those, I genuinely hope that some of the ideas/research that happened in this thread can help point you in the right direction. Good luck and keep us updated! P.S. Quick update since I know I've gone dark lately: my indy shop has been so backed up on problem cars (particularly an old Lotus that's required a significant amount of re-wiring) that they still haven't completed the simple diagnostics that I've been waiting on such as dropping the sump. I've run the math a dozen different ways and the numbers are in favor of a rebuild verses just dumping the car as a roller, but I'm waiting to talk to Jake/RND/EBS/etc until that work is done and I can tell them with more confidence the current state of my engine.

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Based on the above, you might not get a slice of time until the year 2035, lol.

The first thing that needs to be done is checking for bore scoring. This must be done on both sides of the bore, like my part 4 in the bore scoring video series illustrates. Then you need to decide how much you are in LOVE with the car. If anything other than love determines the path, there's no need to call me.

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If I've already resolved not to consider any rebuild option that doesn't include Nickies, does the current level of bore scoring (believed to be little-to-none) even matter since that material would be removed anyway? Unfortunately 12 days of driving isn't enough to know either way on the love question , so I'm forced to choose an option using other means. I know I'm not considering any options that don't give me an engine I can confidently drive well into the future, so I'd be remiss if my decision process didn't include at least a relatively brief chat with you (maybe 20min compared to the usual hour? Basically just long enough to ask a few questions not answered by your website, learn about the latest pricing, and about the current wait list length).

I can answer these here. Our first available completion of an engine for the "Premier Service" (using our most local to you Certified Installer to remove, and replace the engine) is currently October 2020. These engines come fully dyno tested, from our engine dyno. For the "Exclusive Service" (where we collect the car for the full process here) the first available completion is currently March 2021 Of course, pricing matters a lot based on the actual failure that you are experiencing, unless you do have bore scoring. If you do, and the damage is limited to this, with no collateral damages, the pricing starts at 20K for a Stage 1(Premier Service), and goes up steeply from there when someone selects the "Exclusive Service". Of course, we can schedule a chat, but the timeline is usually enough to make the decision for most people to go some other route. I have NO desire to reduce wait times, increase volumes, or make my hand crafted engine, built by a single human from start to finishing something "generic", or easy to get.

Ok, now after three full work days with no contact (well I called for update yesterday morning and the person who answered the phone said he had just arrived and didn't know status of my car but would check and call back but failed to do so). I called this morning for an update . I was told they think they found the problem to be a faulty valve lift solenoid and verified by putting in a known good part and no misfire codes appeared . Recommended replacement of faulty valve lift solenoid $220 for part , also said they are usually replaced in pairs (Now $440) (one for each bank) because the Labor involved is 2.5 hours and if the second original solenoid fails I would be looking at another 2.5 hrs labor. So I told them to go ahead and replace both. Of course they can't guarantee they will cure misfire until installed and car test driven at least 20 miles. Oh yeah, they said the 4 hrs of additional diagnostic I had authorized were exhausted. No mention of whether smoke test for vacuum leaks was ever performed. Now I confess I don't read every forum post regarding mysterious misfires but I've never heard anyone else say , "oh yeah it was the valve lift solenoid" . Anyone else had that issue?

Can't say that I have but time will tell, do keep us posted. Maybe start a new thread with your issues.

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The valve lift solenoid will create a set of misfire codes for one whole bank of the engine simultaneously. You will have P0300 with a P0301,0302,303 or a P0300 with P0304,305,306 together. Anything is possible. What codes did you have?

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Great suggestion. Much agreed. I too suggest starting fresh including previous posts to start a new thread with these issues... Mike

Why didn't they take it for a test drive with the good used part installed to make sure the issue really is the solenoid or let you drive around for a week with it and then replace it with a new one? I really hope they found the problem but this is not how they should have done it. They are still guessing at this point using your wallet.

Thank you Flat6 Innovations, Yes, those were the codes, left valve lift solenoid replaced because it was dead (as well as right one as a preventative and to avoid more labor charges down the road). Codes cleared, car was test driven 30+ miles and no codes reappeared. Misfire problem solved. , happy happy

Quotes source post: 16198608

Yep. I have a �99 where the solenoid cannot be replaced without pulling the valve cover. I paid $3000 all said and done, with lots of diagnostics time and the solenoid itself was $500. My codes were pretty exacting: P1531 or P1530, depending on left or right side, and I had misfires on all 6 cylinders. After the solenoid was replaced, zero codes, no check engine light, all fixed.

Quotes source post: 16200611

So glad to hear this!!!!!!

I feel like i�m having the same issue slightly different. After I had the car diagnosed, Cylinder 6 was getting power but no ground. The mechanic checked the wiring harness and it tested good. He followed the wiring diagram from the injector to the ecu. Said the fault seems like a bad injector driver on the ecu. Sent ecu, immobilizer and key to specialized ecu repair. ecu tested good. They said check the wiring harness. Read this article and was mindblown. Is it possible I just need to check/repair ignition coil ground wires? Are they hard to get to?

^^^^ I hope you get a response from the knowledgeable members here on moving forward with the check/repair. Mike

Anything is possible. You need to check the wiring one pin at a time. If you don't know how, get someone that does. All you need is a mulitmeter and the knowledge how to use it.

Noticed cut ground wires under the seat by the immobilizer. Curious if this has anything to do with the car acting up.

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I think the biggest takeaway from my situation is that bad grounds ANYWHERE in the system can manifest with symptoms almost anywhere else. In my case the bad grounds were for cylinders 1-3 and yet were manifesting on cylinder 5. I don't know how difficult they are to get to since I didn't do the work myself, but my best advice would be to start systematically checking pretty much every ground in the entire car (probably starting with the ignition coils on BOTH banks based on your similarities to my original problem?). Good luck! I'm sincerely hoping that the lessons from my experience lead you to a much quicker solution! As an aside for those who might be curious, here are a couple of pics of my mostly-complete engine out at EBS in Reno: We were originally supposed to be done a couple of months ago but COVID kinda threw a wrench in that plan. The IBD Plenum we've been waiting on just arrived Tuesday and then it'll just be a matter of getting everything put together/installed (including a few extra things I'm having them do on the rest of the car like replacing the viscous coupler because they reportedly tend to burn out by this mileage and preemptively replacing the fuel venturi tube based on Jake's experience when rebuilding dporto's engine) and doing the first couple hundred miles of break-in. We're also still waiting on the accumulator for the UAOS, but we don't have to have it before starting the break-in. They're currently forecasting about 2.5 weeks until it's done and after that I'll hopefully be starting the epic road trip to bring it home via the scenic route!

Fuel venturi tube? You have a picture of this part?

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Do you have a picture that's not out of focus? Hard to see what it and isn't broken.

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Hope this looks better. The five brown wires on the left are taped up and the Five ones on the right where my finger is are taped up with the ends exposed. Im thinking about connecting each one I dont think it matters which one is connected to which as long as they are getting a ground connection?

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Sorry, I don't. I learned about it from this thread where it caused problems on dporto's car while FSI was breaking it in post-rebuild: https://rennlist.com/forums/996-foru...-critique.html From dporto's first post: I think they might get a little more into the diagnostic info later in the thread (IIRC it could have proved fatal for his new engine if not found), but I don't have a link to that handy. Regardless, I don't have any reason to believe mine is cracked, but if this thread and subsequent grenade prove anything it's that this sort of freak failure would be exactly my luck. Especially considering how difficult it was for Jake to diagnose, I just decided to add it to the to-do list from the get-go.

So i swapped out my bosch maf with a $35 maf i got from am autoparts. Car runs great no misfire. I think i got the wrong bosch maf. I think i was supposed to get the no electronic throttle control/no e gas one. Regardless, I feel theres still an issue. Something electrical. I have a performance battery, new alt, even had a fan resistor replacement. If i drive for more than an hour i get a battery drop from 13.4 to 12.6. Sometimes the car dies. Will start right up though.

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Before you connect anything, find the wiring diagram for you car and see if those wires need to be connected at all. They look like they should be connected but to be sure, check against the diagram.

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You might have more than one issue. Since you have a throttle cable this means you have an idle air control motor in the throttle body. This over time can carbon up and cause idling issues. Take it off the throttle body and clean the carbon off it and the port in the throttle body. This should help with the idle. The low idle can cause low voltage readings too so fix the idle and see if that fixes the voltage.

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that i must find and read, so far the ones i seen are confusing. Good news is this site has been very helpful. I have a 996 c2 so now I know I need the maf w/o egas. But after looking into the car I noticed there is a cut ground wire under the passenger seat as well. The passenger seat works other than it cant move up and down. What made me curious about the grounding cables under the drivers seat is that the immobilizer is there and I do have a security issue as well. The car doesnt flash lights when unlocking it beeps after unlock and the red door lock light stays on. Going to work on it this weekend as well as see what that non e gas maf does after install. I appreciate all the assistance on this!

Quotes source post: 16746810

Did that not too long ago, didnt look too bad but cleaned regardless. In the process i split the gasket in half. Its so tiny. So i believe I need to revisit that with a new one. Its a 1999 996 c2 so still looking for the wiring diagram under the drivers seat and waiting on the non egas maf. With the cheap maf i dont get a drop in voltage but i do get these codes: p0112, p0306, p0740, p0102. The same ones I got from my first diagnostic minus the voltage code. All codes pointed to a bad maf according to the mechanic. Will update on how this goes after the new bosch non egas maf and ground wires under the drivers seat research.

That beep means there is a fault when the security system is locking the car. U have to check the filler door, center consol storage, doors, trunk. If the car reads these things "open" it will fault out.

Why are you supplying the mechanic with parts?

Quotes source post: 16757227

that definitely works fine, its when unlocking the car and driving i get a fault. According to mechanic, the maf not working correctly is throwing these codes.

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i didnt supply him with anything but a car to diagnose. I ordered the maf and put it in myself. Mistake I made was not asking him which one to get, and not researching which one is for the 99 c2.

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Was the old MAF tested to know for sure that is was faulty?

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yes. The readings were off so i knew i needed a new maf. I got the egas one, when the one needed was the non egas. What made me bring the car back in was when i got the cyl6 misfire. After time they thought it was a faulty driver in the ecu but the ecu tested out fine. What led them to believe that was the cyl6 got power but no ground. The wire harness was tested and it was good so they thought it was the ecu. Im going to get the non egas maf today and try to check the engine ground strap.

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I had a shop once thoroughly for through my car�s system to test a P1530 code. After many hours, they determined that the ECU was bad or the car�s wiring. But they were wrong. It was indeed a fault of a solenoid. The shop did not know how to test this bad solenoid out, and they didn�t fully understand the impact of a bad solenoid on the rest of the car. My point is only that chasing your tail can happen at a shop where they aren�t true experts on these cars. It�s not rocket science, but it�s also painstaking at times and requires a lot of experience to get it right.

Quotes source post: 16761275

Installed the non egas bosch maf in the 99 996 c2. Few new codes and an old one: p1319 p1318 p1317 p0740 from my mechanics diagnostic the p0740 is being triggered by something maf related(leaning on that answer hard). The other three are interesting. 17 and 18 are misfire/emission relevant on cyl5 and 6 respectively. 19 is Misfire emission relevant. I havent checked the ground wires under the drivers seat yet, but i did look at the engine ground strap by the right rear wheel without taking it off. Looks connected securely. Not able to see where that leads to. With these type of codes is there anything im missing? Is it the ground strap? I thought about the Torque converter clutch solenoid, but before digging that deep i also noticed when turning on the AC, the voltage drops from 13.4/5 to 12.6/7. The car doesnt stall, and the security is back to normal. When unlocking the car the lights blink and on lock they blink. The main key still doesnt unlock or lock but i can open the door and turn the car on. The other key(silver badge, not colorful porsche badge) works great. Took for a brief drive before CEL came on on it is a dream other than a hesitant takeoff. Happy to have the proper maf but the issue still persists and the misfire issue has been recent. When driving the shifting is smooth. Its a tip, the tip seems a bit slower than auto, but smooth regardless. When hitting the gas its almost as if the car believes its on a racetrack and is begging to go so im careful of the revs. Ive never been in a car like this other than when i had a cayenne. The cayenne never had a prob other than the driveshaft and a trans part i got from revmax. After getting those installed($1900 all together) the cayenne was the perfect suv plus the 7700 lbs towing capacity. I do believe this 996 issue is not bad, but definitely needs to be tended to asap. Any thoughts?

Buy a cheap OBDII code reader. You can get one at the local auto parts store. With the new MAF sensor in now, clear all the codes. It will take awhile, driving, for the DME to re-learn the adaptations with the new and different MAF sensor. After driving for awhile, see what codes come back. Have not read back through this thread, but have you changed out your spark plugs and updated the coil packs?

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i have the Actron autoscanner plus. I wanted to get a durametric, but this device proved to be better. I went for a drive yesterday and the CEL Popped up with the codes yesterday. The spark plugs and coil packs were checked, its an electrical issue. I leaning on a grounding issue.

You don't need to delete any codes, the DME will recognize the new part and will make immediate changes and after a certain period of time, it will turn off the check engine light too. You guys are always fixated on deleting the stored codes before the problem is verifiable and fixed. You should only do this after the problem is fixed as a housekeeping and not as soon a new part is installed.

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I didn�t have to delete any codes. When you replace the maf the check engine light is gone. After the drive cycle monitor does its thing the codes come back or they dont. The issue at hand is misfire emissions related codes. Anyone here knowledgeable on that?

I noticed in one thread you stated a new battery was installed. Yet you have low voltage at times. Your problems might stem from something as simple as a bad ground connection. Start where you intially replaced parts. New battery may have damaged, loose post. Ground wire dirty or loose. Check for negative cable fault. Check resistance through cable while bending same. Ground points for coils are on cylinder heads. Ground points for injectors are under dash, driver's side.

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+1

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going to take a look at those because the mechanic did say cyl6 was getting power but no ground. It seems as if somewhere theres a loose connection that needs to be tightened. Might take a look at the fuses too

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Ok so the mechanic did the diagnosis and you are doing the work?

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mechanic did the diagnostics and it led him to believe the issue was the ecu. Cyl6 got power, but no ground. He said the ground is from cyl6 to the ecu. He suggested replacing the ecu. He wanted to try to program another one and swap it out, i told him i will have the ecu tested and i went and got the car. I had the ecu tested and there were no issues. Im currently getting p1317, p0306, p0740. The maf was replaced with the correct non electronic throttle maf and those maf codes are gone.

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Ok, I understand now. Did you check the ground or #6?

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the mechanic says he checked the harness and tested the connection. Thats how he discovered the ground issue. After research here and renntech heres my thoughts as soon as i get time: -check ground by coil where cyl6 is at -check engine ground strap by rear passenger wheel -check the wire harness that connects from alternator to starter(Hear this usually has to do with voltage drops) -check cats Open to any more suggestions

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You don't need more suggestions since already have too many. Time to get your hands dirty and start testing the conductors.

Any resolution to this mystery?

Quotes source post: 16810601

got the wheel off checked ground strap - good connection checked battery - good checked plug by cyl6(behind the wheel behind that plate) good connection pulled coil pack and spark plug, coil pack looks fine, spark plug smelled like fuel but looked normal other than the white part where it says bosch, above the words is was brown like it was burnt? Or is it just normal wear? Cleaned and put back in, drove great. Took it to mechanic he believes his diagnosis was true and that it�s possible the no ground was due to me having the wrong maf in(the e gas, 99 996 uses non egas) which still doesnt address the misfire. He did say he swapped 5 and 6 to see if it was an issue with the coil pack or plug but same problem. Drove home, no cel but rough idling came back, and a slight voltage drop on the way home. Called porsche to get the plug/coil pack, back order will take 5-6 weeks. Called auto parts stores in the area and they can get bosch parts on order within a day. Im thinking swap out all coil packs/spark plugs, and replace. But heres another thing, my mechanic said it was the injector that had the bad ground, is it possible that needs to be swapped and the coil/spark plugs are fine? Im also going to connect those brown wires under the seat, havent got to it yet, not sure if that has anything to do with it but im sure they probably shouldnt be cut. I also will check the wire behind the alternator.

Don't buy any parts unless you are 100% sure it needs replacing or this will get stupid expensive really fast. Put a noid light in the injector connector that you are suspecting to be an issue. Since the coils were swapped and the problem remained at the same cylinder, the problem isn't a coil. Also, since the spark plug is wet, is has no spark or it gets very little fuel from the injector. There is a way to test this too. Start properly testing and stop guessing.

Took my car to euro motors and they did a smoke test. The smoke test lead them to believe the issue is with the oil separator. While taking the car apart they noticed the air pump outlet was previously damaged and it was glued to keep it together. Guess the previous owner was buying time. Unfortunately this pump is $1700. The oil filler tube was also split. Found the part 99660510301 on ebay with a 1yr warranty. Will post update.

So sorry Dex996, can't believe someone would sell a car with critical parts glued back together. Only good news is car should be fine with new parts.

Quotes source post: 16900395

feels good to find the problem, only downside is i cant believe i didnt see it, and i really cant believe the mechanic that has worked on it before hasnt noticed. The air pump is literally right there in front on the left side of the engine.

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How long have you been on the planet? You'd have to very young to find that not believable.

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Ive been here long enough to realize the importance of owning your own tools and using critical thinking skills instead of relying on these pollywogs.

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It's been a long time since I've been suprised at the stuff some people will do.

Just hit up a dismantaler for the sai pump. There r available used and at much better prices.

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Euro Motors corrected the problem. Found a pump from UAS on ebay for $70, they said it was bench tested so i ordered. Breakdown of the parts that fixed the problem: maf sensor $230(Installed myself) oil filler tube $130 aos $160 secondary air pump $70 labor was about $290. after watching countless videos i ended up realizing this job is not hard. The pump is easy to get to, and can even be cleaned if not broken or worn out. The aos takes a little time but can be done without removing the engine. Mine was gunked up. It looked really gross. I could of got the oil filler tube alot cheaper, but that part and the aos were directly from porsche and in stock. No misfires, no problems, No CEL, and the car runs great. Couldnt ask for a better way to spend my weekend, cruising in a 911. Only disappointment i have is before i had misfires issues my own scanner actually pointed out that the AOS and air pump were recently reported. Trust your tools! i have a spark plug, coil pack, and computer if anyone is interested.

^^^^ Glad to hear you found and corrected the problem. Congrats! Mike

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CEL is back!

^^^^^ Mike

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and the code is???