Misfire problem that never ends

[Andy1M3]

2008 E92 M3, manual, single-hump (if that matters)

This problem has plagued the car since March. It ran fine when I parked it for winter storage. When I went to start it up in March the battery was dead. With a new battery it would start, idle for 5-10 seconds, then develop a really bad misfire and die. Eventually it stopped idling at all, and just fires up but starts misfiring immediately.

Codes said crank position sensor, so I replaced that. No change.
Car needed some other work done so it went to a repair shop.
Shop found evidence of water damage in the ECU, that was replaced. (It looks like my windshield gasket was missing some chunks and let water in over the winter). No change.
Injectors rebuilt. No change.
Plugs changed twice. No change.
Coils changed. No change.

They don't know what else to do and want to send it to the dealer. I'd love to tackle this myself but I am super swamped at work and don't have the time.

When you clear the codes, it starts and runs normally for 5-10 seconds, and then the misfires progressively start and get worse, leading to it dying after ~20 seconds. Subsequent starts are plagued by misfires right away.

Anyone have an idea what could be to blame?

[Redd]

What are your misfire codes? Remove the entire plenum and run the car without. If the misfires go away you may have a vacuum leak somewhere.

Also check your ground strap and check for exhaust leaks.

[e90sanmarino]

Are you using OEM coils? The aftermarket ones dont seem to work on our cars.

Also Id recommend buying new injectors as opposed to rebuilding them. Especially when our injectors are known to hydrolock the engine when old.

[spammysammich]

You need a shop that has ISTA to run the misfire detection test to minimize the parts cannon guessing game.

[Andy1M3]

Thanks for the responses.

There was a smoke test done that found no vacuum leaks.

The last time I ran the codes it came up with almost everything, this was assumed to be related to the ECU water issue. After that was fixed the shop took it over so I am not sure about what codes are left.

OEM coils were used.

Injectors - good to know.

The car is currently at a BMW dealer. I hope to have some more answers next week. Best case scenario they can diagnose it and I will update here for anyone in the future going through the same issue.. hopefully they can save some money!

[RocketyMan]

Originally Posted by Redd

What are your misfire codes? Remove the entire plenum and run the car without. If the misfires go away you may have a vacuum leak somewhere.

Also check your ground strap and check for exhaust leaks.

This doesn't do anything. I'm not sure why you give this advice when there are individual throttle bodies per cylinder on this engine. This is a calculated speed density engine via T-map sensor. Any vacuum is created AFTER each individual throttle plate and communized through each "idle strip" where the sensor determines vacuum. (Any flow through plenum is negligible/irrelevant)



https://www.realoem.com/bmw/enUS/sho...diagId=13_1241

[Redd]

Originally Posted by RocketyMan

This doesn't do anything. I'm not sure why you give this advice when there are individual throttle bodies per cylinder on this engine. This is a calculated speed density engine via T-map sensor. Any vacuum is created AFTER each individual throttle plate and communized through each "idle strip" where the sensor determines vacuum. (Any flow through plenum is negligible/irrelevant)



https://www.realoem.com/bmw/enUS/sho...diagId=13_1241

I give this advice because I spent 2 mths chasing an all cylinders misfire issue a couple years back. Tried everything - O2s, sparks, smoke/water test multiple times, all showed no issue. But the misfires persisted. In the end, I removed the entire plenum - engine running in alpha-n mode - and misfires went away. So I managed to localize the source of the problem - a vacuum leak somewhere in the plenum.

In the end, the leak was caused by some broken tabs in the IAT sensor hole. It would only leak under high engine vacuum, hence it passed all smoke tests.

AFAIK, S65 MAP sensor is pre-TB before the plenum. So any vacuum leak after the MAP - eg in the plenum - can cause misfires.

[smokinjoe64]

Originally Posted by Andy1M3

2008 E92 M3, manual, single-hump (if that matters)

This problem has plagued the car since March. It ran fine when I parked it for winter storage. When I went to start it up in March the battery was dead. With a new battery it would start, idle for 5-10 seconds, then develop a really bad misfire and die. Eventually it stopped idling at all, and just fires up but starts misfiring immediately.

Codes said crank position sensor, so I replaced that. No change.
Car needed some other work done so it went to a repair shop.
Shop found evidence of water damage in the ECU, that was replaced. (It looks like my windshield gasket was missing some chunks and let water in over the winter). No change.
Injectors rebuilt. No change.
Plugs changed twice. No change.
Coils changed. No change.

They don't know what else to do and want to send it to the dealer. I'd love to tackle this myself but I am super swamped at work and don't have the time.

When you clear the codes, it starts and runs normally for 5-10 seconds, and then the misfires progressively start and get worse, leading to it dying after ~20 seconds. Subsequent starts are plagued by misfires right away.

Anyone have an idea what could be to blame?

Experienced similar multi-part, multi month chase to solve misfires. Like many shared, there's a plethora of possible causes with a decades plus S65.

After spending $$ in parts/labor, 'trips, fumbles and stumbles' => camshaft position sensors replacement did the trick...been runnin' great since.

Of course, those along sh** load of new parts [sample of a few below]

[RocketyMan]

Originally Posted by Redd

I give this advice because I spent 2 mths chasing an all cylinders misfire issue a couple years back. Tried everything - O2s, sparks, smoke/water test multiple times, all showed no issue. But the misfires persisted. In the end, I removed the entire plenum - engine running in alpha-n mode - and misfires went away. So I managed to localize the source of the problem - a vacuum leak somewhere in the plenum.

In the end, the leak was caused by some broken tabs in the IAT sensor hole. It would only leak under high engine vacuum, hence it passed all smoke tests.

AFAIK, S65 MAP sensor is pre-TB before the plenum. So any vacuum leak after the MAP - eg in the plenum - can cause misfires.

No. That's not how speed density works. The MAP sensor is connected to the idle strip which is communized AFTER each throttle plate...hence--vacuum.

Did you even review the link I posted?

[Redd]

Originally Posted by RocketyMan

No. That's not how speed density works. The MAP sensor is connected to the idle strip which is communized AFTER each throttle plate...hence--vacuum.

Did you even review the link I posted?

Regardless of how things should work theoretically, I'm sharing my real world experience. Take it however u want to.

[RocketyMan]

Originally Posted by Redd

Regardless of how things should work theoretically, I'm sharing my real world experience. Take it however u want to.

Thank you for sharing your anecdotal experience.

[Redd]

Originally Posted by RocketyMan

Thank you for sharing your anecdotal experience.

Instead of picking on my advice, why not offer some to OP on how he can solve his issue. Based on facts and how things work, of course.

[RocketyMan]

Originally Posted by Redd

Instead of picking on my advice, why not offer some to OP on how he can solve his issue. Based on facts and how things work, of course.

Easy. It has already been mentioned prior by spammy as oppose to non-fact/data based guesses.

Originally Posted by spammysammich

You need a shop that has ISTA to run the misfire detection test to minimize the parts cannon guessing game.

[Andy1M3]

Just heard from the dealership, they replaced both throttle position sensors assuming that was the issue. Net result is misfires on all cylinders. Waiting to hear their next steps. I don't have time to work on this thing myself but the lack of information is really frustrating. Any ideas?

[tdott]

Might not be the same issue, but this is what I did to troubleshoot a car with similar issues.

https://www.m3post.com/forums/showthread.php?t=2067525

[yardbro]

Originally Posted by Andy1M3

Just heard from the dealership, they replaced both throttle position sensors assuming that was the issue. Net result is misfires on all cylinders. Waiting to hear their next steps. I don't have time to work on this thing myself but the lack of information is really frustrating. Any ideas?

Silly of them to go this route only to end up with getting nowhere. Unfortunately, I expect nothing less from the dealer.

Without you having any codes or data to share with us I don't think anyone on here will be able to provide any beneficial information. If at all possible, get someone to scan this car when you have time or post some stuff from the work order the dealership would have given you. I'm certain you'll get more helpful responses.

[RocketyMan]

Originally Posted by yardbro

Silly of them to go this route only to end up with getting nowhere. Unfortunately, I expect nothing less from the dealer.

Without you having any codes or data to share with us I don't think anyone on here will be able to provide any beneficial information. If at all possible, get someone to scan this car when you have time or post some stuff from the work order the dealership would have given you. I'm certain you'll get more helpful responses.

100% agree. Need actual codes from a legit scanner along with data. Preferably ISTA.

Poor performance from a typical dealer. You have to think about the technology from s85/s65 circa 15-20 year old car and the caliper of techs available.

As mentioned before, this is starting to look like a parts canon guessing game.

[Andy1M3]

The update from the dealer is that they're reaching out to BMW engineers to try to diagnose this. Not sure about that.

I've asked for the codes to share with a buddy I know and this is the photo I've received. I assume you guys need some better info from ISTA to try to diagnose. Please let me know what else you need and I'll get it.

Also if anyone has a recommendation for a shop in the Montreal area please let me know.

[RocketyMan]

Originally Posted by Andy1M3

The update from the dealer is that they're reaching out to BMW engineers to try to diagnose this. Not sure about that.

I've asked for the codes to share with a buddy I know and this is the photo I've received. I assume you guys need some better info from ISTA to try to diagnose. Please let me know what else you need and I'll get it.

Also if anyone has a recommendation for a shop in the Montreal area please let me know.

Okay. So this is helpful.

I question ALL coils and ALL spark plugs. Doesn't make sense every single cylinder is misfiring.

Needs to be stock NGK 4471 spark plugs--gapped to about .032" or 0.8mm torqued to 23 NM and OEM coils. Pictures of these two things would help.

[spammysammich]

Originally Posted by RocketyMan

Okay. So this is helpful.

I question ALL coils and ALL spark plugs. Doesn't make sense every single cylinder is misfiring.

Needs to be stock NGK 4471 spark plugs—gapped to about .032" or 0.8mm torqued to 23 NM and OEM coils. Pictures of these two things would help.

Would a big leak at both exhaust collectors create misfires due to O2 sensor discrepancies?

[RocketyMan]

Originally Posted by spammysammich

Would a big leak at both exhaust collectors create misfires due to O2 sensor discrepancies?

The symptoms the OP is describing seems like a combination of plugs/coils problem as it's an immediate start-up problem. It usually takes some time for the O2s to heat up as well as coolant to get to minimum temp with run time for the DME to attempt to go into closed loop. But as far as mis-fire detection strategy, the DME starts this as soon as it can.

Were you thinking if the donut gaskets were bad at the collectors?

[spammysammich]

Yes.