Car rolled in gear now misfiring

Hey folks, Here's an interesting problem. I know I'm probably in for a major tear down and rebuild, but I'm curious to see what others think might be going on here. I've attached a Durametric screenshot below. Background: 2003 996 with 211,200 miles! I bought it cheap knowing that I would have to invest in a major rebuild and refresh at some point. Car actually ran great until I had a mishap backing it up on ramps to do some work underneath. Basically, I didn't make it all the way up the ramps, the car stalled in reverse and rolled down the ramps about three feet in reverse gear. I started it again and the car immediately began misfiring on all the Bank two cylinders. I'm wondering if I rotated the engine backwards slightly and something got messed up with the variocam plus system? Symptoms: Misfire codes (p0304, p0305, p0306) , valve lift codes (p1360, p1362, p1364) and O2 sensor codes (p1106, p1108). Basically the car is running rich on Bank two. Short and long term fuel trims are at .8 and the O2 sensor codes seem to support that. The car mostly misfires below 3500 rpm, and is most affected by light throttle. It actually still runs and pulls strong when pushing it hard, which is amazing to me. It's mostly at idle or light throttle that it misfires. The durability of these engines and the engineering that keeps it running despite some major issues is impressive. I know I'm probably crazy for still driving it but I'm having an interesting time trying to sort this out. I drive it hard for an hour or two at a time, and I even took it on a 800 mile road trip to Santa Fe and back last week. Haha. Like I said I know I'm in for a major rebuild soon anyway. Fixes I have tried: Replaced alternator & y-cable (charging voltage was low). Replaced Bank two variocam solenoids (both lift and timing solenoids), replaced coil-packs and plugs. Smoke tested the intake and fixed a few vacuum leaks. Replaced cracked oil filler tube. Replaced cheap catalytic converter on Bank 2 with an OEM cat. So any guesses as to what's going on here? Variocam? Timing? Lifter damage? Dual mass flywheel damage? Bore scoring? It seems variocam or lifter related due to the 3500 rpm cutoff for the misfires, so I've tried the various remedies we all know about (replace solenoids, Durametric variocam activation, ATF in the oil!) The misfires actually do seem to be improving the longer and harder I drive it. That just might be the ECM is adapting but the physical problem is not going away.

Show your short and long term fuel #s and graph your o2 sensor on that side. It may be as simple as a bad o2 or a bad injector. The issue with rolling back cant hurt a variocam....its not how it works. Maybe a healthy dose of seafoam fi cleaner? There r simple test for the variocam soleniods too if u sesrch u will find them but u guess u replaced them. Did u check continuity on that harnes back to the dme?

I don't know but I'd bet heavily on something happened to the tensioner or variocam

Try changing out your coils on bank 2 - if you want to just test them, try swapping with bank 1 coils and see if the misfires follow� It could be purely coincidence that the misfires happened after the mishap on the ramps.

Thanks. I�ve poured a couple bottles of Techron in over the last few fill ups. I�ll graph the O2 sensors. I know that the voltages swing from .8 to .2 but mostly hover around .8 I did replace the pre-cat sensor on that bank. The long and short term fuel trims are both around .8. Normal should be 1? so I think it�s running rich and pulling fuel? I�ll take a pic of those values. I haven�t tested the Variocam wiring back to the DME. I do know that I can activate both banks using Durametric. it�s so curious that it acted up right after rolling, so just makes me wonder what got damaged. Oil scavenge pump, affecting oil flow and pressure on that bank? or maybe it�s all a coincidence.

Replaced all coils and plugs in that bank. I�m wondering about the variocam pad too. Are those black plastic? I found some black plastic bits in the sump. I know the PO had those and chain guides replaced a couple years ago.

Erase all codes, reset the ECU by disconnecting the negative battery terminal for 30 minutes. Reconnect the battery and go for a drive. See if the codes come back during your drive. Remember it will take some drive time for the ECU to adapt.

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Like with De Jeeper said, the rolling forward in reverse and the car stalling wouldn't necessarily damage any valve train components. This is like when you're on a hill at a stop light and the car rolls back slightly and then when you start to go, the car stalls because you overreacted and didn't release clutch properly. It's embarrassing, but it usually just means restarting the car. Now, you have the 3.6L 3-chain engine that does NOT have the VarioCam VVT chain tensioner like found on the 5-chain engines; instead, it has a camshaft vein cell adjuster. Therefore, there are no wear pads to change out on the variocam+ system. You do however, have chain guides that could wear out and need to be replaced. That's why it's always good to check the camshaft deviations using a Durametric scanner. Personally, instead of just replacing just one bank of coil packs, I'd advise you to replace ALL coil packs and plugs. That puts you at a nice base line. Then, reset all codes and complete a drive cycle and report back.

Thanks. That's an interesting tidbit about the vein cell adjuster. I've seen animations on how it works but didn't notice the lack of a tensioner. My camshaft deviations are 3.80 Bank 1 and 1.70 on Bank 2. I'm starting to feel better about potential mechanical damage and will dig deeper into the electrical stuff. Replacing coil packs on bank two is an interesting idea. Is there a way to verify timing in the Durametric software? It appears that the green camshaft plugs on bank 2 are at the front/bulkhead side of the engine, so a little tough to clearly see with the engine in the car.

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Those deviations are still within Porsche tolerances which is < 6 degrees of deviation. IMHO, it's always good to replace all coil packs/plugs as a general rule of thumb. I just did it last week when cylinder6 decided to melt my coil pack. I replaced the whole kit and cabootle and the car is now purring like a kitten.

It's actually called a "vane cell actuator". I have fixed engines that had valve timing skip due to being rotated backwards. The VW VR6 with the first generation chain tensioner is somewhat notorious for this....

Yea, what has happened is that your exhaust cam on bank 2 has advanced 1 tooth.. With over 200K your chain has worn and grown in length so the tensioner is extended pretty far..The tensioner doesn't have a "ratcheting lock" so just residual oil pressure . This engine is not supposed to be rotated backwards due to this. With 3 cylinders on each cam, there are 3 places the cam will resist rotation and 3 places it will rotate on its own...When rotating backwards the oil will be pushed out of the tensioner and the chain will have enough slack to skip a tooth.. The cam sensor is on the Intake cam so as far as the DME is concerned the cam timing is OK... But with the exhaust cam on back 2 advanced 1 tooth the engine will not be smooth due to every other cylinder has different exhaust cam timing opening the exhaust valves too early.. I've played with cam timing a lot back in my old Super Stock days...you would be surprised how much you can change cam timing....some cams have 50-60* difference but they are on all cylinders...You can't have a smooth running engine when half the cylinders have a different exhaust cam timing.. Put the engine on TDC and lock the crank, pull the scavenge pump from bank 2 and the tensioner, check the timing of the exhaust cam. You can probably just rotate/skip the exhuist cam on the chain back a tooth and put it back together in about an hour...

Original poster's : the car stalled in reverse and rolled down the ramps about three feet in reverse gear. I started it again and the car immediately began misfiring on all the Bank two cylinders. That means the rolling back caused the misfire. And new quote Porschtech 3: Yea, what has happened is that your exhaust cam on bank 2 has advanced 1 tooth.. There is the connection.

And to fix that, you actually need to drop the engine, and re time the Variocam Plus. But with over 200K miles, and you were already planning on a rebuild, this is now the time to do the rebuild. No more procrastination.

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Why would the engine need to be dropped?

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I even heard it called a "vane phaser" or "VVT phaser". In my Porsche book that came with my 996, Porsche calls it a "rotary vane pump" (see image), but I think it's called "camshaft adjuster" in the OEM parts catalog. Lots of people refer to the 5-chain camshaft tensioner as the camshaft actuator. Whoooosh... This is why I shouldn't rush through through original posts when I'm heading out the door for work. I totally missed the part when the OP stated he had the reversed gear engaged when the car was moving backwards off the ramps. I guess I was thinking maybe he quickly pressed the clutch pedal after it stalled, which of course, would cause the car to roll back. I've stalled manual cars all the time backing up on incline, but always remembered to quickly press the clutch along with the brake to avoid rolling the opposite direction. Learning to drive manual as a kid was a painful experience. My dad would take me to the steepest hills to train me how to start from a complete stop in 1st. Keeping it from rolling back and not stalling was nerve racking. After I got pretty good at it, he taught me how to "pop the clutch" to get my ol' 1963 Ford F100 to start. haha! Great times!

Yup that�s right. Rolled forward three feet in reverse gear. I assume the engine rotated backwards a little bit. What could go wrong?!? 😏🤔 My dad taught me the same way, sometimes doing donuts in my high school parking lot to learn winter driving. Been driving a clutch for 40 years but this happened pretty quick and caught me by surprise. Don�t be dumb like me! I�m

Thank you! I actually did some reading about retiming the exhaust cam and watched a couple videos, thinking that this might be the issue. i think I can do it, but may be back with a few questions. Steve

This guy had an interesting way to set the exhaust cam timing on bank 2. Essentially loosen the bolts on the exhaust camshaft sprocket, then use the cam timing tool to rotate and nudge the camshaft back into position. Doable with the engine in the car? Starting at 3:56 on the video: You Tube Thanks

That guy only had to move the exhaust cam a small amount..... I think the problem you will have with that method is that the slot is not long enough to move a full tooth... You need to move the exhaust cam counterclockwise a full tooth, I'm sure I could do it in the car through the scavenge pump hole with the tensioner out...BTW you will have to remove the A/c compressor to access the tensioner. You may as well start watching some video-s on that too. A lot of people struggle with that first time...

Ok thanks. I had the AC compressor off a couple weeks ago so I�m familiar with how fiddly that is. Looks like 32mm socket to loosen the tensioner What tool should I use through the scavenge pump hole to rotate the camshaft? That seems preferable to messing around in the tight spaces at the front of the engine. BTW I think I�ll be buying an Ultimate AOS soon. 👍

I would use a chisel that fit the drive for the scavenge pump and a wrench that fit the chisel shank to turn the cam.. I would mark the chain and both gears first before removing the tensioner and keep the crank locked/pinned..Then remove the tensioner and try to make the exhaust gear jump over a tooth back to where it was......then verify the timing ...it should be back with the slots lining up through the two small holes in the front..

Ok that�s clever. Last question - am I loosening the four bolts on the front of the camshaft sprocket when I do this? Or do they stay tight?

I would not loosen those 4 bolts, I would put it right back where it was. If you get it all F**Ked-up by letting the chain slip on the "crankshaft" ( where it is not marked or you can even see), then you will need to start over from scratch, and that will mean loosening those 4 bolts and the intake cam bolt, and get a new intake cam bolt, and you will be in a mess...lol

Ok this all sounds serious so I want to make sure I get this right. As I visualize this - Since the tensioner will be off the chain, there will be enough slack in the chain to rotate the camshaft sprocket *inside* the chain and basically move a tooth back one link in the chain? We don't want the chain to move with the sprocket, correct? We're basically replicating what happened when the engine rotated backwards, but in reverse. Am I kind of lifting the chain off the sprocket while I rotate the camshaft, or is there enough slack that it will rotate without moving the chain? This is what I'll likely see, except this is a 5-chain but ...

What i dont get and it can be because its a 3 chain motor is that the cam deviations r fine. Doesnt the sensor read off the exhaust cam? Should he not see an issue in his telemetry in one of the many timing calcs that durametric broadcasts? Also should he be able to visually check the timing is off with the set up tool? I would deff do this before u try to jump the chain.

So I thought about it and this is what I would do. There is no guaranty that it would work because it all depends on the positions of the four bolts holding the exhaust cam sprocket in place. But this is how I would do it on the number of Ferraris with similar issues. Find TDC overlap bank 1. That is where you start so you always know how to get back there. From that position, turn the engine crank shaft one full turn and you should get to TDC over lap bank 2. Right before you get there, slow down and stop when the exhaust cam slot can fit in its vertical position perfectly. This is where you need to be. Lock it with the tool. Loosen the four holding M6 bolts on the exhaust sprocket so the cam stays put while the chain, the exhaust sprocket and the intake cam can move with the engine. Carefully turn the crank shaft (only a small amount is needed) to 1) where the intake cam slot is perfectly vertical and can fit the timing tool. Inspect the crank shaft pulley to make sure that it's also in the TDC overlap position. When all those positions are found, reinstall the four holding bolts on the exhaust cam. Undo the tools, turn the engine over 4 turns, check that all cam positions are lined up. That is how I would do it. Access to all the places on bank 2 sucks but it sucks as it is now.

Thank you. You're right, there would have to be enough room for the sprocket to move in the correct direction relative to the bolts. This is similar to the procedure this guy used when the timing slipped doing his IMS: https://forums.pelicanparts.com/pors...-pls-help.html "The relative position of the exhaust cam (lower cam) to the IMS, and there fore the crank is fixed and does not change. It is only the relative position of the intake cam (upper Cam) that changes. So if the bottom cam is not straight up and down (use a straight edge and the joint between the cover and the head to check this) than the timing of that cam is off. I can give you a fairly simple way of adjusting this. To turn the crank take off the serpentine belt and use a socket on the main pulley. The engine rotates clockwise looking from the rear of the car. Try to turn it in that direction if you are going more than a few degrees. First get the engine close to TDC for Bank1. Then rotate the crank until the exhaust cam is straight up and down. Now loosen the 4 bolts on the exhaust cam sprocket (this assumes you have removed the scavenger oil pump to have access to these bolts). Now you can rotate the crank to TDC, this should only be a few degrees, without rotating the cam. Once the crank is at TDC and the cam is still straight up and down re-tighten the bolts on the sprocket ( I tighten two of them, then put some Loctite blue on the other two and tighten them, then remove the first two and put Loctite on them and put them in. The torque for these bolts is in the manual." And I think the same discussed here: https://www.986forum.com/forums/perf...iming-m96.html Access to the cam plugs on the front / firewall side of the engine does suck, but I need to start there anyway to verify if the timing is screwed up as suspected.

Good questions. I believe the camshaft sensor is on the intake cam (as mentioned above), but not sure if that is what's used to calculate cam deviations. Also I would love to know which metrics (besides camshaft deviations) to look at to determine if the relationship between the intake and exhaust cams is correct. Either way, definitely going to check current timing first via the green plugs

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Cam sensor is only on the intake side because only the intake cam timing varies as in when the valves open and how much they open. The exhaust cam shaft does not change its timing with respect to the crankshaft. Also, the intake cam position would be the only one used in calculating deviations, while assuming that the timing of the exhaust cam is spot on. The only indication when the exhaust cam is out of time is that it does not run well, misfires, and a CEL is thrown up.

Yes, check the cam timing first to see where your at and look to see if the bolts are indeed in the center of the slots like shown in your pic. If they are then you probably have enough room to loosen them and turn the cam the distance of one tooth to correct the timing.. But if the bolts are at the edge of the slots already as I have seen before sometimes you will not have enough slot to correct the timing without "jumping the chain on the sprocket" like what happened when you rotated the engine backwards.. The 3 chain engine is worse about jumping the chain when rotated backwards because the chain only wraps around half the exhaust sprocket and half the intake sprocket or about 90*, where as in the 5 chain engines the long chain only wraps around the exhaust cam only and wraps almost completely around the sprocket as shown in your pic..There is a separate short chain that connects the exhaust cam to the intake cam..5 chain engines are not bad about jumping the chain when rotated backwards, I rotate mine backwards all the time ... Yes the Cam Position Sensor is on the intake cam and is used for cam deviation and checking/calculating vario cam function..The DME has no idea where the exhaust cam is, it just assumes.....

Thanks for all the great info! I think I have a plan for the week. I�ll take pics and report back on how it�s going.

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Hey Steve, I watched the Rokket YouTube video your referenced and he leaves out a lot of vital information for timing a 3-chain M96 engine. I would say this video should have been titled, "How to correct slight cam misalignment on a M96 engine" or something like that. IMHO, if you were starting from scratch and used this video to time an M96 engine after valve train assembly and camshaft installation, you would screw the engine up. In all fairness, he does explain a lot of good information about the serial number matching of the heads, cam cover, and journal bearing caps and their proper orientation, etc. That being said, if you're ever planning to time a freshly rebuilt engine, I strongly recommend following Jake Raby's procedures. You don't necessarily have to purchase the entire series. You can purchase just the engine timing - Stage#16 from Amazon Prime. Amazon Amazon All the best!

Hey thanks! Yeah I�m definitely a fan of Raby. I�ve studied a few m96 rebuild & timing videos and it does seem fairly involved. Not sure if I will do a rebuild myself or just have a shop do it. I have the desire and interest just not the facilities to do it well. If anyone in Colorado with a shop is looking to help with a DIY rebuild let me know! 😉 First things first, I need to figure out this exhaust cam timing issue and see where the car�s health is at. I think I�ll still pick up a bunch of the Raby material to just better understand these engines. I have a rudimentary knowledge but more is always better! Thank you Steve

Quick update on this ... I put the engine in TDC overlap cyl 4 and pulled the green cam plugs. I can confirm that the exhaust cam on bank 2 is out of time. I'll add some pics below but they probably won't add much value. So, to get the slots in the exhaust cam to line up vertically with the case, I actually have to rotate the crank about 30 degrees PAST TDC, which I believe means the exhaust valves on bank two are opening late. Sussing out my logic here ... To perform the gentler, "secure the exhaust cam, loosen the bolts on the sprocket method", I think I would have to rotate the engine backwards to get all the other cams timed up with the screwed up exhaust cam. I don't really think I want to do that ... So I think my only option is to go with Porschetech3's idea, which is to loosen the chain tensioner and try to jump the cam sprocket back a tooth, or two. That or just pull the cam cover, remove the cams and re-time bank two. Can anyone confirm my logic here? Here's the exhaust Cam at TDC (overlap cyl 4). And the position of the crankshaft when the exhaust cam slots are vertical.

Your logic is good here. Looks like you are only out by 1 tooth.. Mark the chains/gears/bolts where they are... If the 4 bolts are in the center of the 4 slots on the exhaust cam gear, you may enough adjustment to get the cam lined up, if not then you can put it back to your mark, then remove the tensioner and jump the chain a tooth.... and put the tensioner back.. When you think your got it right, rotate the engine clockwise at least twice then check the timing again..

Ok great thanks. I am messing myself up looking at the mirror image of the exhaust cam slots The camshaft needs to rotate clockwise when looking at sprocket under the oil scavenge pump right (from the back of the car)?

Yes.. Have you removed the scavenge pump yet? where are the 4 bolts in relation to the 4 slots...? pic?

I haven't taken off the scavenge pump yet. Waiting for a new pump o-ring and the cam lock tool. I'll do it later tonight or tomorrow morning. I might actually try rotating the cam using the cam lock tool from the front of the engine (like the rocket guy in the video). Seems to be about the same amt off as his demo.

Ok......my Son always says he doesn't need new tools because he hasn't figured out all the ways to misuse his old tools yet....lol

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Believe me I'm definitely doing the chisel and vice grips method from the scavenge pump side if the first way doesn't work out. Pics of that for sure to document the insanity.

Ok got the scavenge pump off and bolts are centered on the sprocket. However, there really is no way to turn the camshaft at the front the engine using the cam lock tool. Just not enough room. Unless I invent a tool! So ... I think I'll have to do it from the back, sprocket side. It occured to me I can't really loosen the sprocket bolts because it doesn't seem possible to turn the camshaft through the sprocket slot without turning the sprocket itself. Unless there are some novel ideas here ... I think we're back to your (Porschetech3's) original idea of just removing the tensioner and skipping the sprocket ahead one tooth.

Welp, pulled the AC compressor, and all the related junk around there to get to the bank 2 chain tensioner. Tensioner is out, but still doesn't seem like enough slack in the chain to rotate the cam by hand from the scavenge pump sprocket. I just can't get the muscle on it to turn it. I think I'm in for about a $3k bill to drop the engine and have it re-timed. Or just spend $25k to rebuild the dang thing.

IMHO, you should be adjusting the slight misaligned exhaust cam from the opposite side, not the sprocket side. See images.... Notice the colored red side of the half moon cam ends? The right half moon is offset from left side. That is done for reason so that you know the correct phase of the cam. They both should match. I would think by loosening the sprocket's 4 bolts, you should have enough adjustment to bring is close if not perfect in alignment.

[QUOTE=b3freak;18678213]IMHO, you should be adjusting the slight misaligned exhaust cam from the opposite side, not the sprocket side. [/QUOTE=b3freak;18678213] Yeah I have thought of that. The exposed cam slots for bank two are at the front of the car and bitch to get to and get a tool in there. I'd have to invent something that would fit in that space and still give you enough leverage to turn the cam. This pic with the mirror kind of illustrates the issue. There is just enough room to slip a 3/4" thick mirror in there.

You don't have to "muscle" it to get it to jump the tooth, you just have to "finesse" ALL the slack to around the exhaust cam gear while keeping the chain taught around the crank and up to the intake cam........

Just for anyone curious about this... You Tube

Success! I ended up loosening the bolts on the scavenge pump sprocket and rotating the exhaust cam back to its correct position. I modified (used an angle grinder) the cam lock tool to fit the cam slots at the front of the engine. I could not for the life of me pull any slack in the timing chain to rotate the sprocket ahead a tooth per Porschetech3's suggestion. Too tricky with only the space through the scavenge pump hole to manipulate the chain. Plus not having the ability to lock the intake cam on bank 2 made me really nervous about trying to slip the chain around. So ... loosened the four bolts on the scavenge pump sprocket and the exhaust cam actually rotated on its own to find its resting position. I assume a couple of the lobes were resting on the lifters and it just rotated to its natural position for TDC. I nudged it with the tool so it was perfectly aligned with the case seam and the intake cam. I know I'm at the end of my travel on the cam and sprocket, so no more eff ups! Will have to wait for a rebuild to put it all back to normal. I rotated the crank 12 times to verify timing was still ok (checking all the slots on bank 1 and 2 cams). Put everything back together, disconnected the battery for a while to reset the DME, said a prayer and then fired her up. She ran really smooth! Plugged in Durametric to verify CAM deviations and misfires (none!). Changed the oil and then took her for a drive. Ran sooooo good. Pulled strong and everything was smooth. Cam deviations were 2.00 left and 0.94 right, which was actually a bit better than before! I do have two codes P0491 and P0492 for the secondary air pump, so I need to recheck my vacuum lines after moving stuff around, but waaaay better than it was. I call bull**** on the indy shop in Colorado that insisted my misfires were due to bore scoring and insisting that the engine was in time. Discovered that the green plugs were never pulled to check that. I don't doubt I might have some scoring at 211,000 miles and she's a little tired, but it definitely was not the cause of the misfires. Anyway, planning to run her for a bit "as is" out of curiosity to see how much further a 211,000 mile engine will go, and save up for a rebuild with Nickies down the road. For now, she pulls strong and runs great. These engines will actually put up with some abuse and try to keep running despite some problems. Hopefully I haven't fried any exhaust valves or exacerbated bore scoring by letting her run like this for a bit. Thanks everyone for the diagnosis and troubleshooting!! I'm grateful to have dodged a bullet and have learned a lot. Steve

It took you long enough I could have had that fixed and on the road in an hour ..(j/k) This is how you fall in love with a Porsche product. You get your hands dirty, learn a lot about the way they are built/engineered, save a sh*t ton of money, then get to enjoy the drive .......Then when you DO have to dig deep into the pocket, you don't mind....

Well done. I am so tired of hearing about stupid shops, crooked shops, incompetent shops. Do it yourself !!!

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Haha thanks for nailing the diagnosis! That really put the pieces together for me. To be fair the car is in my shop 30 min away so that accounted for a bit of delay and multiple trips back and forth. Next time, I would definitely be faster! It only took me 1 1/2 hours to put it all back together. Experience is cumulative.

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I agree ... That's the only way to educate yourself. I was planning on spending $25k with them on the rebuild, but if they couldn't be thorough on this diagnosis, it makes me question how thorough the rebuild would be. So they probably lost my $

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If I were you I would drive your car back to that shop and explain that you fixed it yourself. Let them know you are/were disappointed with their diagnosis and that you will take future business elsewhere . No reason to be confrontational just explain calmly what you feel . Maybe ......... Just maybe they will think twice in the future . Congratulations on the repair !

�I call bull**** on the indy shop in Colorado that insisted my misfires were due to bore scoring and insisting that the engine was in time. Discovered that the green plugs were never pulled to check that. I don't doubt I might have some scoring at 211,000 miles and she's a little tired, but it definitely was not the cause of the misfires.� No surprise there�

Hooray! I�ve been following this thread and am super happy for you! This is a great forum.

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Hey thanks! I'm glad to share the resolution. Often these threads start and there is no conclusion, leaving everyone hanging. This is great forum with tons of collective knowledge and wisdom.

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Fixed it for you.

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100% I was just the instrument of many great ideas.

To be totally fair :: This was a VERY unusual problem that seldom ever happens and is difficult to diagnose due to the DME has no idea where the exhaust cam timing is because there is no Sensor on the exhaust cam , and fault codes sending the diagnosis in the wrong direction.. In a case like this you have to go back to "old school diagnosis": and use fault codes with a grain of salt... I was Top Trouble Shooter in Dealerships since the early 80's and these were the kind of things that got sent to me after everyone else gave up... So I don't fault the shop for not being able to find this one....( Yellow Cab is right, too many fingers get pointed at shops being incompetent) AND a LOT of this success goes to the OP for being so detailed in his background of the event and the symptoms, and being able to follows advice and sticking with it. If it had been someone with less wherewithal this would have been another one of those threads that got left hanging...( the car would have gotten sold, traded off, a new engine ..ect) Glad it was saved....enjoy !!! .....Put some more miles on that baby and see how far it will go....

Here is another very unusual case of a GT3 that had low power.. It had been on a Dyno and at 3 different Indy shops and 3 Porsche dealers and was fixing to be "bought back" by Porsche if it couldn't be fixed... There were no fault codes ( except sometimes it would set cam timing codes, but cam timing was perfect)........Various Sensors were replaced, Cam timing was checked and re-checked multiple times, compression test, cylinder leak down test..ALL tests showed good but engine was down on Power.... Then it was sent to me as a last chance before being bought back or an new engine ( customer was running out of patience).. This is what I found... Ring on flywheel had slipped The ring on the DMF flywheel has slipped.....it is a 60-2 ring......... The way I verified the problem was I removed the #1 coil from the plug and installed an "old school plug wire", then hooked up an "old school timing light" and shot the ignition timing and compared it to the Digital Computer Timing and seen that the Digital Computer Timing was marginally off from the Old School Timing Light, so I removed the DMF and ordered a New DMF to compare....The difference was remarkable...

Interesting,freezer,oven type interference fit?…..good catch.

I'm not very mechanically inclined but man after reading this thread it makes me want to be! Amazing experience in this forum and it's the best one on Rennlist.

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Yeah these guys on RL are serious gurus with decades of experience. Porschetech3 - I love the old school way of diagnosing the flywheel problem. I remember setting timing using a timing light back in the 70s on an old Toyota. I still have my Dad's old Sears timing light - still works! Have you ever seen a DM flywheel cause misfires? I saw an instance where a guy with a 997 had that problem. I was about to go down that rabbit hole next with mine.

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Exactly ......yea that pic got sent around to all the Porsche "Hot Line" Engineers to be on the look-out...I don't know if there was ever another one that had done this, or if this was the only one...I wasn't privy to that info..

fantastic news. glad you were able to get it sorted! PorscheTech3 MVP!

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Yes I have seen DMF's cause misfire codes.... I have also seen "rough roads" cause misfire codes.....but In the case of rough roads causing the misfire codes it was due to the software program being too sensitive....The fix was updated software... FWIW :::: the missfire monitor is less Sensitive when new or after clearing faults...then after adaption and as the monitor "learns" it start to become more Sensitive....On some Cayenne's after clearing faults, the missfire monitor is so insensitive it won't even register a "dead miss"...

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Yea, PorscheTech3 deserves all the MVP credit. All I get these days is PMs telling me I'm a troll and "stay in my lane" comments. Maybe I should change my username to PorscheTechB3. ha!

It's hard to believe you get targeted for being helpfull. I have seen you post novels of helpfull advice to first time posters , and the videos of Jake are even more helpful.. "You can be my wing man anytime as Maverick says" ( or on my "B" team .)

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I'm in! WOOT WOOT! But I have one concern.... You Tube