Another Wonky Idle/Stalling Thread

1999 C2 with ~101k miles, 6MT. Hi all, I'm in need of some help and I'm going to put as much information as I can in here in the hopes that the combination of all of this makes sense to someone and can help me figure out what's wrong. I've been chasing down an issue over the better part of 6 months and I'm really trying to lean hard into analysis of it so that I don't continue throwing parts at the problem. That being said, I have replaced a LOT of things to date. I've owned the car since 2020, and the biggest job I've done is an engine-out to do the IMS, RMS, Variocam pads, any gaskets/seals I could think of, and many other things. Without further ado, here it is. The Problem On a cold start, while warming the engine for about 10-20 seconds, the idle will drop from its ~1200 cold start idle, and sputter down to ~500 and either come back up or stall, independent of me doing anything like hitting the gas. Restarting the car usually works and the car will run without issue. This part of the issue is intermittent and random and I cannot say for sure whether it happens more frequently when I am below a half tank of gas (more on why that matters a little further down). It also smells awful like it's running overly rich. On a hot engine, independent of ambient outside temp, I will clutch-in while coming to a stop and I see the idle dip below the regular idle speed of ~680RPM and either sometimes come back up and fluctuate, or the car will stall. This has happened with either the AC on or off. Most recently, I have noticed that this tends to happen when the gas tank is at half full or less. Even though that's been the most recent development, I BELIEVE the car has stalled at any other point in the fuel gauge, but I've replaced many parts so it's possible those were also problematic and resolved things to a degree, as the car has ran much better. The latest stall happened at 1/4 tank while I was on the way to the gas station. I filled up the gas, and I have yet to see a stall again. Upon filling up the car, I noticed it ran MUCH smoother. I am currently at half a tank. I can keep running it down and see what happens. CEL Codes P1123 Oxygen Sensing Range 1 Cylinder (1-3) P1125 Oxygen Sensing Range 1 Cylinder (4-6) Replaced Parts/Diagnosis Crank Position Sensor (2023) MAF (2023) Fuel Filter (2023) All 4 O2 Sensors (2023) AC Recharged After Engine out (2023) Intake was smoke tested in November and found minor leaks - fixed; and again 2/9/2024 - no leaks this time ICV Cleaned with carb cleaner and tested with 9V and ground to pins to see the doors moved freely. TB was cleaned as well. Engine Out from 2022-2023: UAOS IMS Solution/RMS Thermostat/Waterpump Variocam pads Banks 1 & 2 All Fuel Injectors (that seem to be discontinued now): https://lnengineering.com/new-afterm...280150455.html Upper & Lower chain pads Cam chains Vacuum lines with Y fittings AOS Connection Piece on Bank 2 Plugs/Coil Packs Durametric Numbers Read out was done on a nearly hot engine: Oil Temp 76* C Engine RPM: 680, Stable Range 2 Cyl 1-3 FRA: 0.90 Range 2 Cyl 4-6 FRA2: 0.92 Range 1 Cyl 1-3 TRA: 0.0 (I have also seen -0.34/-0.37 TRA/TRA2 on another run and I think that was a colder temp at 46* C) Range 1 Cyl 4-6 TRA2: 0.0 Camshaft position 1 Deviation: 0.0 Camshaft position 2 Deviation: 5.0 (why wouldn't this be 0.0? It's within spec, but did I not time Bank 2 right after replacing the variocam pads?) Oxygen Sensing cylinders 1-3: 0.98 - 1.02 (fluctuates) Oxygen Sensing cylinders 4-6: 0.98 - 1.05 (fluctuates) Fuel Pressures Here's where it may get interesting: Prior to start: 48PSI (stable) Running: 45PSI (stable) Revving to 2000: ~53PSI, drops to 40PSI and stabilizes at 45PSI Engine off: Drops from 45PSI to 35PSI and then climbs to 48PSI within a minute Engine off for 1 hour: 44PSI Engine off for 3 hours: < 10PSI If I'm to understand correctly from whatever is out there on the internet, a 1999 C2 should have idle fuel pressure at 55PSI? If someone can confirm what it is really supposed to be, that would help. At this point, I am leaning toward something in the fuel system but something still doesn't seem right. The fuel pressure does not really fluctuate at idle so that potentially means the FPR is fine. The pressure is generally low (need to confirm that) so that could mean fuel pump; but, a fuel pump usually just dies and doesn't have low-pressure pumping issues. It certainly smells very rich at startup so I am not sure why a failing fuel pump would cause a rich condition. I can provide more screenshots/pictures/info you need to get a clearer idea of what's going on. Any help/thoughts are appreciated!

When have you cleaned your ICV (idle control valve) and TB? Seems you are leaning towards a fuel pressure problem but it could just be a gummed up ICV.

The cam.deviations do look suspect but i dont think this is your issue. The 2 things i would go after first is cleaing the idle air orifice in the tb and do a smoke test in the intake. Your o2 values r going high so the computer is adding fuel probably cause by an ait leak. U can kind of see this in the short term fuel troms but as they should be closer to 1. Although your fuel pressure is also a suspect at the pressure ranges u r posting. Low fuel pressure can wrek havok on the o2 and idle quality. Check the first 2 because u dont have to buy parts and then maybe replace the fuel pump.

I forgot to put that on there but yes I did clean the ICV with carb cleaner and also applied 9V and ground to the pins to see that the door inside it moved freely. I also smoke tested the intake yesterday and I can see no leaks at all. I have seen leaks before and fixed those, but the issue remains. I�ll update the original post.

I can remember what the maf range is suppose to be but u cam look it up. I would graph it through the rpm range and then back to idle. There was a rash of bad maf sensors last year even though they were all bosch certifided.

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So to do this, wait until the engine is hot, read out the durametric value and hit the gas?

Quotes source post: 19271242

yes even a couple hundred feet down the street so u "load" the motor. See if the sensor falls out of range.

U could always remove amd inspect the fuel pump. There have be instances that the internal tubes have split and since your issues r when the fuel level is low its a possibility. Its pretty easy to access

Quotes source post: 19271276

↑ THIS ↑ But if it were me, @ over 100,000 miles, once i open that fuel pump hat... I'd just replace the pump and the lines as needed. Old lines do split, especially with our current modern high alky fuels. You've got the easier to do 2wd simpler fuel pump/lines system.

Fuel pressures on your 99 seem to be okay. The static pressure will be 55 psi., running pressure around 45 to 47. Seems a little counterintuitive to think there�s a fueling malfunction when trouble codes indicate over fueling based off of O2 sensors. OP states there�s a fuel smell on cold start. Also car might stall when fully warmed up. Sounds as if cats are compromised in some way. Try to log voltage of post cat sensors. Then post findings if you can. Also MAF readings should be 15 to 17 KG per hour at idle and voltage should be around 1.4

The TRA reading here is the KEY....The reading of 0.0 is not plausible and was probably due to clearing the fault codes, that re-sets them to 0.0 ... The previous readings of -0.34 and -0.37 means the TRA went full lean trying to compensate for a RICH condition.... This is happening on both banks, ( P1123 P1125 )the two most common things I have seen to cause this is MAF Sensor and Fuel Pressure regulator "leaking fuel up through the vacuum hose" Pull the vacuum hose off the fuel pressure regulator while running and see if it has fuel in it....( not while engine is extremely hot for safety sake) I know you replaced the MAF, but what part number did you put on and was it a Genuine Bosch MAF? But rest assured the engine is running RICH and most likely doesn't have a vacuum leak... Edit :::FWIW Codes P1123 and P1125 can be either Rich or Lean , it depends on if the TRA went negative (-) or positive...in the PIWIS, the fault code is accompanied by a subtitle that says either "above" or "below" and can get real confusing, but just looking at the TRA for a negative ( -0.36) or a positive (0.36) will keep the confusion down..

Quotes source post: 19271708

TMI ?

You can never have TMI !

No sir! Testing right now but running into issues with Durametric and my laptop. Plus it�s hard to figure out how to take readings while driving 🤣

One thing I am thinking of doing is running it down to 1/4 tank again and seeing what that does to my fuel pressure.

Quotes source post: 19271708

This kind of makes sense to me. And, does running rich with negative tra and 0.9 fra, below 1, steer away from air leak as well as fuel supply insufficiency? In other words it is unlikely to be a fuel pump or fuel line problem? Seems like pulling the vacuum line from the fuel pressure regulator would be a quick test to evaluate a leak there. Hadn't thought of that before.

Quotes source post: 19273898

More like just enough info to maybe fix it... So, if the FPR diaphragm is leaking ( fuel ) into the vac line, wouldn't a faulty diaphragm also cause the FPR to malfunction in maintaining correct Fuel Pressure..?

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I had an issue a year or so ago and while my fuel pressures were fine, Skip suggested that I change the FPR. Lo and behold, it did have a slight leak when I popped the hose off of the old one.

Quotes source posts: 19273924, 19273910, 19273978, 19273986, 19274222

Duratmetric can "Log" several PIDS at once so you don't have to watch them while driving. But the main thing you want to see is the TRA after driving a while at very low RPM ie Range 1 which is close to idle and where your fault codes are showing up at... Sometimes I wonder if my posts are understood... Yes, you are correct, with a fault code and negative TRA and FRA under 1 , the problem usually is not an air leak or fuel supply unless there is more than one problem.... Not necessarily, if the leak in the diaphragm is small it will not effect the high pressure readings( but will effect the TRA near idle speeds), and if the leak in the diaphragm is large there is a good chance of flooding the engine or Hydro-locking with fuel......( I have seen quite a few engines Hydro-locked from a faulty FPR..) ... FPR's can also fail from mechanical issues like weak or broken internal springs or blockage that will effect the pressure readings.... I remember your case .... FWIW :: on the DME 5.2.2....... the "Oxygen sensing" is like the "short term fuel trim" on most other ( domestic) cars, and the TRA is like the "long term fuel trim" but only near idle speed ( Range 1) ...and the FRA is like the "long term fuel trim" in the load range ( Range 2) ... The TRA is expressed in "milliseconds of injector time"with a fault code set-point at +-0.36ms..The normal injector on-time is about 2.40 milliseconds ( ms) , if the "oxygen sensing" is spending too much time above lamda 1 ( like 1.03) , the TRA will start to pull time from the injector and when the injector on-time gets down under 2.04ms the fault code is set...and the TRA value will show -0.36 meaning is has taken away 36 milliseconds from the injector on-time...

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Not sure i understand them completely, but sure trying...!!! thank you.

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Yes, the DME 7's are different, the newer DME's have a wider window of adjustments and more ranges of trims......The "long term fuel trim' in the Range 1 near idle is expressed in % instead of ms, and is called RKAT not TRA,.....The "long term fuel trim" in the Range 2 load range is divided into an upper and lower, FRAO and FRAU instead of just FRA But basically they still are just trying to keep AFR at near Stoichiometric/Lamda 1 ( 14.7 AFR) for best emissions/economy, then will go to a better AFR for power under full throttle and ignore the 02 Sensors... IF you get confused on the RICH/ LEAN, you can always watch the readings while forcing the system to Lean by creating a large vacuum leak, then watching the values, or by forcing it go RIch by add in some propane fuel then watching the values, this also will check the system for function....

@Porschetech3 I wonder if you could help, 99 996, replaced plugs, coils, injectors, MAF, AOS and this week the FPR. Smoked and no leak found, latest inH2O 5.24. Oxy sensing 1-3 1.02, 4-6 1.00 FRA 1-3 0.82, 4-6 0.76 TRA 1-3 -0.14, 4-6 -0.14 whats causing the TRA�s to be below 0.00. Thanks

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You say you replaced injectors? Did you use the $300 OEM Early model injectors or the later 3.6 less expensive ( and slightly richer) injectors ? The engine is running very slightly rich ( but is acceptably in range) The TRA reading of -0.14 on both banks is only "half way" to the set-point of -0.36ms to set a fault code..So is in the adjustment range and will not set a fault code... No engine is perfect and you will never see one at a TRA of 0.00ms ( after it has ran a while) BTW :: your engine is "not actually running rich".. The DME is adjusting it to "Stoichiometric ", but it would have been if not for the "closed loop adjustments"..

Hi, got the new aftermarket 996-606-120-01 injectors from LN 51.75 each.

Quotes source post: 19356331

Your fine ....IF the injectors were 0.14ms "leaner" there would be no need for the DME to adjust, .......but like I said, no engine will be "perfect" and you will never see a 0.00ms TRA....

Thank you 😊

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Your welcome .!!

I had no intention of ghosting this thread btw. Life took priority but now I am back on this. I am trying to replace the pressure regulator. I can�t seem to get it out of its housing. I removed the clip and it rotates but I can�t get enough leverage to pull it out. Any tips or tricks to this?

I just replaced mine, if you get a small screwdriver and lever it out on both sides where the clip goes.

I got it! Thank you. I�ll update this thread when I�ve had a chance to plug in the durametric and read some values. My hunch is that it didn�t change anything because the first start was rich (albeit didn�t smell as bad as all of the previous ones), followed by idle hunting when I turned on the AC compressor. It didn�t stall and I was able to take a few laps and it ran great.

I need some more help, 996.1, starting the car cold after sitting overnight, it idles fine, however adding throttle the engine hesitates, almost dies before revs increase, driving straightaway it will hesitate from time to time when accelerating until the engine is up to temperature. Once up to temperature everything is fine, start, idle and acceleration all through the rev band. All numbers are good, Mass Air Flow, FRA�s, TRA�s etc. smoke test is good, inH2O good. New, plugs, updated coils, fuel injectors, AOS, FPR & new fuel pump two days ago. Prior to replacing the fuel pump, pressure with pump on 49psi, engine running 45psi, after replacing the pump, pump on 54psi, engine running 46psi however the pressure drop over time was approximately the same, down 10psi after 30min, 15psi after an hour, 25psi after 2 hours, 35psi after 6 hours and to zero after 8 hours. Question, where could the pressure be leaking and starting with zero pressure in the fuel manifold, would that account for the early running problems. Thanks.

Maybe look up the FPR - fuel pressure regulator. It might need to be replaced as noted above.

Put in a new FPR last month, no change, that�s why I then replaced the Fuel Pump.

Hesitation on accelleration cold is normally caused by a lean bias in the fuel system. Exactly what is your FRA #'s during cold start/run?

@Porschetech3 thanks, I�ll check the FRA�s in the morning when it�s cold and been sitting for 12 hours and post them.

Hi, FRA�s straight after start cold: Range 2 Cylinder 1-3 = 0.88 Range 2 Cylinder 4-6 = 0.81

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What are the TRA values?

TRA�s 1-3 = -0.18 & 3-6 = 0.18

Sorry 3-6 = -0.18

Yeah, the fuel trims are OK, and with no fault codes, I would clean the MAF Sensor...When the Maf Sensors get dirty they are more likley to run bad cold, the dirt insulates the "hot film/wire" in the Sensor whereas a clean sensor reacts quicker to airflow/temp..

Thanks, I�ll do that, it is a newish MAF sensor 1600 miles ago, I have the old one which I�ll also try. I did notice the EGT after the CAT is always low 126 �C.

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Oops. I think I've been doing this wrong. I was under the impression these values could be retrieved after a drive with the engine off and would be representative. In other words they represent a cumulative adaptation to the oxygen sensor readings. Are they constantly changing by the minute or by the second? Does it even make sense to look at values after a drive with the engine off?

Quotes source post: 19404130

Just pull a big vacuum hose off and watch how fast the trims change.... The "Oxygen Sensing" will respond right away, and just in a couple of minutes the "TRA "will follow... Sure you can look at the trims with engine off, they will be at whatever value was last used when running...

Ok, update here. I changed the Fuel Pressure Regulator per @Porschetech3 . Interestingly, as the old one started to warm with the engine, it would start releasing a slight fuel vapor through the vacuum hose (not sure if that was normal or not). There�s good and bad in this update: The car�s battery died over the winter effectively wiping out the DME mappings as it went completely flat for several weeks. I started the car prior to changing the FPR and observed idle wonkiness. I then changed the FPR. On the new FPR, I�ve gone 250 miles without a stall or any idle wonkiness. The car idles and runs the best it has in a while. The RPMs will drop predictably on every single clutch in. They drop and settle flat right around 600-700 which makes this next part a mystery. After 250+ miles, the CEL came on. Same codes, P1123, P1125. Here are my cold start fuel trims/MAF: Air mass: 23 kg/h FRA Bank 1: 0.93 FRA Bank 2: 0.94 TRA Bank 1: -0.37 TRA Bank 2: -0.38 Here are those same numbers after driving around for a few miles, at operating temp: Air mass: 15.75 kg/h FRA Bank 1: 0.85 FRA Bank 2: 0.86 TRA Bank 1: -0.21 TRA Bank 2: -0.19 Again, new FPR, new MAF (from a few months ago). Why did I still get a CEL and seemingly running rich? Was that perhaps a fluke from starting it off a battery reset with the old FPR? Should I suspect injectors next? Edit: I have reason to suspect my injectors which are new. I purchased the LN �new aftermarket� injectors which have seemingly disappeared from their website since last year.

I�m wondering about the new fuel injectors I got from LN in April�23, ever since then I�ve been getting CEL and 1123, 1125, 1129 from time to time and TRA�s between -0.14 to -0.38. A lot is new, plugs, injectors, coils, MAF, 02 sensors, AOS, FPR & fuel pump. Another interesting observation, after changing the AOS, straight after start I got between -4.94 & -5.24 inH02 however if left connected it increases to -15.86 when warmed to normal operating temperature. It was suggested that may be caused by valve guide wear and to replace the oil with straight 50 weight and see if that still happens.

I received a response from LN�s support (Stephen): It seems this would most likely be the issue. Edit: I should have researched it more, being that a pack of all 6 costed somewhere around $270, whereas new OEM are $100+ a piece. I�m not an injector expert by any means.

@Outatimemk Your TRA fuel trims were out of spec ...-0.36 is the CEL set point for TRA .....if over +0.36 or under -0.36 the CEL and code will be set .. Good info on the issue with the new injectors.... it would not have been high on the list of possibilities...

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@mccahey Your AOS is defective !! You should NEVER get a reading above - 6.0 inh2o ....High ( vaccum) readings can only be caused by malfunctioning AOS Regulators... Low ( vacuum) reading can be caused by vaccum leaks. or poor ring seal/high blow-by from the engine...

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Where do I go from here? Unfortunately I tossed my old injectors. Who knew a 3 inch piece of plastic could be rebuilt? Whats the next best/reliable source of injector? I�ve been reading about the 3.6 injector swap but it seems these things have increased in price as well to $100+ a pop new.

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I replaced my injectors last month with new ones. I removed white Bosch ones. The new ones were blue Bosch. Part number 0280156053 at 54eur per injector (3.6 engine).

What's the flow rate for the 3.4 injectors? PPH or CC?

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UGH! I'm in the exact same boat right now. There are no vacuum leaks (smoke tested), but it throws 1123 and 1125, and sometimes it stalls when coming to a stop (clutch depressed, RPMs drop, and sometimes stalls). Unrelated to this, I replaced the fuel pump, regulator, and injectors about nine months ago with those ~$300 no-name ones from LN Engineering.

Quotes source post: 19449996

It could be those injectors, or maybe it could be a MAF, like Porschetech3 alluded to in post #11 https://rennlist.com/forums/996-foru...l#post19271708

As a general anecdote, it�s seemingly harder to find replacements for the 3.4 (the fatter blue ones), and it might be a good idea to do a 3.6 swap (the skinny white ones) anyway which is the way I am leaning. Gotta say, this kind of sucks. All the prices have gone up and I don�t know if there�s a single trustworthy product out there.

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It could be multiple problems like in my case. The FPR likely resolved my stalling issue. I also replaced my MAF and did a DME reset (full battery disconnect/death). I�ve gone nearly 300 miles at this point without even coming close to stalling. The codes seem unrelated and are probably the injectors. I almost want to say that replacement of the crank position sensor made me go from stalling every day to stalling once a week (but that�s probably my imagination)

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Disconnect the SAI pump and see if the stalling continues.

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What's the reasoning? To my knowledge, my SAI system is working correctly -- it turns on for a short bit after a cold startup and again for a few seconds a minute or two later. The stalling occurs infrequently (about once every 100-200 miles) and happens whether the engine is hot or cold. Given that LN has acknowledged the injectors are an issue and their willingness to credit me for the cost, I'm leaning towards the injectors being the cause but willing to be proven wrong. In the meantime, I'm data logging every trip. For context, all of the following were replaced (not due to this issue, just as preventative maintenance for being @ 131k mi and the PO deferred some maintenance): fuel filter fuel pump fuel injectors fuel pressure regulator UAOS oil filler tube alternator, battery, and starter o-ring on brake booster to plenum connector intake manifold and plenum gaskets

If the SAI pump is seized or binding it puts so much load on the alternator it can stall the engine. The SAI sometimes comes on for a moment when coasting to a stop, just when the fuel cutoff allows fuel in again.

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Have you tried a DME reset? Disconnect the battery for a few hours or leave it overnight or something like that. I do wonder if that actually fixed my issue because yours sounds a hell of a lot like mine, maybe more so than anyone else�s story I�ve read across the forums.

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Yes, I did a full reset about 1500 miles ago after I replaced the fuel pump assembly. It took about 1000 miles before it threw a code (1123 first, then 1125), but the infrequent stalling when coming to a stop was still there.

Quotes source post: 19451719

That makes a lot of sense. Instead of unplugging it, I might try triggering it with the Durametric (if possible) while the engine is idling.

A few questions for the experts: 1. Should I not drive the car if it is running rich? Am I at risk of scoring otherwise healthy bores on a stock 3.4? 2. At what point does the DME say �enough is enough� and stops trying to trim the fuel (negative TRA)? Or does it never do that? 3. I�ve noticed there is 1 issue that hasn�t gone away contrary to my statement earlier that the car is running great now: Shortly after a cold startup, the car seems to stumble (it could be 30-45 seconds after startup or so). The idle will drop and I�ll get a VERY thick smell of fuel when this happens. After the FPR replacement, it stabilizes without stalling. This doesn�t happen on every cold start. It�s random. What could this be?

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I remember from the Tony Callas video on fuel trims he said the DME will only adjust the injector timing +/- 0.4ms. When the DME adjusts TRA to +/- 0.36 the CEL comes on. You Tube I might have something similar going on (more evidence we're in the boat here). Immediately after a cold start, if shift into gear (within about 5-10 seconds) and apply throttle a bit (just enough to back out of the garage) the engine doesn't have the response I expect (car doesn't move according to the throttle input I'm giving) and wants to stumble a bit but doesn't stall. If I wait another 10 seconds, it's fine.

Remember guys , that "Oxygen Sensing Range 1" is NOT referring to O2 Sensors , it is referring to "fuel trims" by sensing oxygen and codes 1123 1125 can be either rich or lean ( in PIWIS it also gives an above and below indication ) meaning meaning the ferl trim has reached its rich or lean limit... BEFORE YOU CLEAR ANY CODES read the TRA value to see if it is -0.36 ( lean limit reached meaning it is running rich) or 0.36 ( rich limit reached meaning it is running lean )..

I ordered a set of GB injectors from FCPEuro slated to arrive June 3: https://www.fcpeuro.com/products/por...ing-85212197kt I�ll tackle Bank 2 shortly thereafter and see if it hopefully fixes the richness on that bank before proceeding to the next one.

I have a set of genuine Porsche injectors on order from FCP. They arrive next week. In the meantime, I drove to my other place and picked up my Durametric and smoke tester. I'm going to double-check for a vacuum leak and then pull fuel trims, oxygen sensors, and MAF readings. The OBD dongle and Torque app are only giving me fuel trims as percentages.

Later model engines have the low speed/idle fuel trim expressed in % instead of ms ...so the +- 0.36ms set point/limit for the CEl is equal to +-6%

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Please correct me if I'm misunderstanding or if my math is wrong... In Tony Callas's video, he said the minimum/maximum possible adjustment is +/-25% (+/-0.4ms), and the baseline was 2.0ms. That would make +/-0.36ms equal to +/-18%, right?

Quotes source post: 19457198

No, the 25% he is referring to is the "Oxygen Sensing" or "Short term fuel trim"......that is just the quick adjustments , when they reach their limits it doesn't set the CEL, it moves the TRA/RKAT either richer or leaner..( long term fuel trim near idle) The TRA is expressed in ms on the early cars ( +-0.36 ms set point ) Long term fuel trim near idle The RKAT is expressed in % on the 2000 -2008 ( +- 6% set point) long term fuel trim near idle

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Ah, got it. I really appreciate the clarification.

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I have the exact same issue, currenly with my indy trying to diagnose it. Please let me know if you find anything!

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See if you can find out about where your injectors came from. Our issue is very likely the LN �new aftermarket� injectors.

I just double-checked for vacuum leaks... and sure enough, I have a very small leak at the shaft seals on the resonance flap.

Quotes source post: 19471549

I would venture a guess that after 20+ years of service that ALL M96/7 engines will have a slight leak at the resonance flap shaft seals. ( if it already hasn't been sealed ) Sealing the resonance shafts would be a good idea on ALL of them that hasn't been done...

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There�s a cheap, effective, and easy fix. Rarely do those three things ever get uttered in the same sentence, especially with a Porsche. Search my username and you�ll find it.

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I found your post yesterday after I discovered the leak. I ordered a 19 mm silicone cap that I'll use to seal off the leak.

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Yes, you came up with a nice little "Gold Nugget"

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Would it be odd if I framed your comment on my garage wall?

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Be my guest !! I try to remember all the gold nuggets I have came across in my 50 years in the biz , but I'm not a journalist ( my oldest sister was ) so I don't write/post about them usually...

Bank 2 came out pretty easily (without lowering the engine. Disconnected cyl 4 injector after the rail came out in case anyone�s wondering. Here�s a comparison of new OEM 1999 Porsche injectors on left vs LN �blue� injectors on right. Spray patterns are different and there�s no notch for the bracket on the LN.

Replaced injectors. I did not lower the engine at all. This wasn�t too bad. I found that the wire for Cyl 3 coil pack needed to be routed over the rail, not under it and I was able to lift up the rail in bank 1 and prop it up on the expansion tank while I replaced them. Verdict is the car doesn�t seem to run rich at startup. I think I didn�t install the intake correctly at first and it threw P0150 on the first run. I reinstalled it and the car runs better. Here are my values: Oil Temp: 85.5 Oxygen sensing Bank 1: 1.00 Oxygen sensing Bank 2: 0.98 FRA Bank 1: 0.90 FRA Bank2: 0.91 TRA Bank 1: 0.13 TRA Bank 2: 0.16 So, do we think we got it? I am not sure. I reset the fault memory and will drive around and see what happens. Although, this seems to indicate it�s not running rich anymore.

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Yikes, that must be tight. Did you remove the intake plenums?

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I didn�t need to. I did certainly cut up my hands, it wasn�t easy in that regard. But certainly doable without lowering engine or removing plenums. I probably have small hands. Just drove around for 10 miles - this thing runs great now. I will check cold start tomorrow and we�ll see if I smell fuel.

Well, how did it run on cold start? QUOTE=Outatimemk;19485987]I didn�t need to. I did certainly cut up my hands, it wasn�t easy in that regard. But certainly doable without lowering engine or removing plenums. I probably have small hands. Just drove around for 10 miles - this thing runs great now. I will check cold start tomorrow and we�ll see if I smell fuel.[/QUOTE]

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[/QUOTE] Sorry I didn�t update. I�ve driven about 300 miles since the injector job. No more rich cold starts or any fuel smell. Cold start idle drops are fine - settles at 800-900 when cold. No more stalling. No more idle dips. No more codes. When warm, the RPMs drop and settles flat in the middle of the 600 and 800 RPM ticks, and right around 800-900 with the AC on. The engine seems to run smoother as well, less �shivery�. So, lesson learned - don�t try to save a buck buying cheaper injectors even if LN is the one selling it.

I wonder if that is my issue. I have the P1123 zero vacuum leaks. Have the LN injectors

So interesting. Those were very close to my numbers if you take a look through all my posts. Same with the code. Your bank 2 is not as bad so it didn�t set the P1125 code (you need to hit -0.36 according to @Porschetech3 ), but still running rich. Change your injectors. I got OEM from FCPEuro and paid the full $600 for it. It sucks, but � I didn�t want to get burned again.

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I thought I saw you say that LN gave you a refund. is that correct?

They gave me a gift card (or coupon code) for the amount I paid to them, however, they don�t stock the OEM 1999 injectors. It�s ok because I will eventually buy from them again.

agree. that was nice of them. I appreciate all the help!

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apparently I just got the last set in US original from local porsche dealer. $114.00 each plus I�ll get the 10% pca discount.

@Outatimemk everything still running smooth after those new injectors?

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So far so good. 300+ miles I think, and no codes, no rich running, stalling etc.

I am going to start installing the new injectors tonight. wish me luck!!

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new injectors installed. Perfect cold start! Night and day difference overall! Thank you for this thread!!

Sorry to dredge up an old thread; I just wanted to add that I had the same symptoms with the blue aftermarket injectors. I swapped them back to OEM, and it's running much smoother now.

My 4.0 rebuild has occasional misfiring and hesitation at low engine speeds. I also have issues with hot start where I get misfires at idle but runs fine off idle for a minute after start up. I am using the LN Chinese injectors and am wondering it that is the problem. (I don�t think they sell these anymore). I have gotten a lot of check engine lights for O2 sensors. All are new. Now it�s misfires. Runs like a raped ape at high rpm above 2k.