[SOLVED] When hot - misfires in idle and rough idle

SvenHz · 12-28-2021, 09:26 AM

Quote:

Originally Posted by NiBe

I replaced all coils with Bosch. This is after first drive, around 10km. Long story short no change.

Did Bimmerprofs/you check the lambda probes? All I can think of is that something is up with those.

NiBe · 12-28-2021, 03:24 PM

Quote:

Originally Posted by SvenHz

Did Bimmerprofs/you check the lambda probes? All I can think of is that something is up with those.

Hello, all lambda probes are new.

NiBe · 12-30-2021, 09:53 AM

Still trying to figure this out. I'm now assuming that the fuel trims issues are not a cause but a consequence and that the real cause are misfires. When I reset adaptations and drive the car from my home I always drive +- 5 km downhill, mostly engine braking and I always get one up to three misfires.

What can be reason for misfire when engine braking? What is specific to engine braking that could cause a misfire? Under load the car does not misfire.

NiBe · 12-31-2021, 05:59 AM

Hi,

today I tried Ista D. I did various tests and two are interesting.

Injector test - result - replace all injectors. It has to be somehow wrong as I have all index 11 new injectors.

Throttle body. Here is a video:

Seems to me that the result was no passed because two reasons:

Reason 1: Angle 90 was not reached

Reason 2: Voltage dropped below 5V

Do you agree? This might be the root cause. What do you think?

Moreover this testing generated fault codes which are attached.

NiBe · 01-02-2022, 09:56 AM

Here I recorded what the car does in neutral.

As you can see it easily generates 200 misfires when in neutral. I was never able to get misfire when the engine is under load.

What do you think?

I don't think it is cylinder specific as now it generates misfires on cylinder 3, some time ago it was cylinder 1 and before that cylinder 2..

Btw why RPMs go up while throttle angle is constant? (look around 2500- 300 RPMs)

NiBe · 01-18-2022, 11:47 AM

I sorted it out! However I'm not 100% sure what was the solution. In my last maintenance I did:

1) replaced all lambdas (although they were new installed by shop)
2) found and fix a small (like toothpick) leak in exhaust ~20cm after downstream lambda
3) connected ISTA-P which updated DME (however to the same version as it was before, done by winkfp)

Car is like new now. Now the learning fuel trims process works. The car has more power, is smoother and more smoother every driving session (as it learns) and idle is also smooth.

Quite happy that this is over

Thanks for all suggestions.

SvenHz · 01-27-2022, 03:40 PM

Well done! Are your Learnbits okay if you look in Inpa? Also for the long term, check for error messages periodically. Especially the NOx system is sensitive.

NiBe · 02-19-2022, 03:45 PM

Quote:

Originally Posted by SvenHz

Well done! Are your Learnbits okay if you look in Inpa? Also for the long term, check for error messages periodically. Especially the NOx system is sensitive.

Hello!

Everything is OK since the fix. No errors, fuel trims OK, learnbits OK. Hope that it will last long

Thanks for you help!

NiBe · 04-25-2022, 05:20 PM

To complete the story. The problem reappeared after approx 3 months. I did contact Bimmerprofs again and after few INPA recording he told me that I have leak in exhaust and referenced this his article: https://bimmerprofs.com/n52b30-probl...ulating-probe/
And he was right. I was able to confirm a small leak in exhaust. In my "fix" 3 months ago I already fixed one leak of exhaust but apparently not properly so this time I changed the flexpipe completely and it changed everything. It was quite difficult to confirm the leak as it was very small. I tried soapy water method - nothing, smoking into exhaust - nothing. What helped me at the end was a vacuum cleaner connected to tail pipe and at the same time smoking around the exhaust around suspicious areas and looking if the smoke is sucked into the exhaust. In my case smoke has been sucked via flexible part of my flex pipe. Not much but it was apparently enough the confuse DME resp. postcat O2 sensor that the air/fuel mix is lean resulting in a too rich mixture (spark plugs black) and other problems as described in the thread. Btw after the fix my MPG increased by 10%.

Very glad that Bimmerprofs helped me he really knows what he is doing.

12-30-2021, 09:53 AM	#25
NiBe First Lieutenant 452 Rep 364 Posts Drives: BMW E91 & E92 Join Date: Nov 2021 Location: Europe iTrader: (0)	Still trying to figure this out. I'm now assuming that the fuel trims issues are not a cause but a consequence and that the real cause are misfires. When I reset adaptations and drive the car from my home I always drive +- 5 km downhill, mostly engine braking and I always get one up to three misfires. What can be reason for misfire when engine braking? What is specific to engine braking that could cause a misfire? Under load the car does not misfire. Last edited by NiBe; 12-30-2021 at 10:05 AM..
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12-31-2021, 05:59 AM	#26
NiBe First Lieutenant 452 Rep 364 Posts Drives: BMW E91 & E92 Join Date: Nov 2021 Location: Europe iTrader: (0)	Hi, today I tried Ista D. I did various tests and two are interesting. Injector test - result - replace all injectors. It has to be somehow wrong as I have all index 11 new injectors. Throttle body. Here is a video: Seems to me that the result was no passed because two reasons: Reason 1: Angle 90 was not reached Reason 2: Voltage dropped below 5V Do you agree? This might be the root cause. What do you think? Moreover this testing generated fault codes which are attached. Attached Images
	Appreciate 0 Quote

01-02-2022, 09:56 AM	#27
NiBe First Lieutenant 452 Rep 364 Posts Drives: BMW E91 & E92 Join Date: Nov 2021 Location: Europe iTrader: (0)	Here I recorded what the car does in neutral. As you can see it easily generates 200 misfires when in neutral. I was never able to get misfire when the engine is under load. What do you think? I don't think it is cylinder specific as now it generates misfires on cylinder 3, some time ago it was cylinder 1 and before that cylinder 2.. Btw why RPMs go up while throttle angle is constant? (look around 2500- 300 RPMs)
	Appreciate 1 Soden82477.00 Quote

01-18-2022, 11:47 AM	#28
NiBe First Lieutenant 452 Rep 364 Posts Drives: BMW E91 & E92 Join Date: Nov 2021 Location: Europe iTrader: (0)	I sorted it out! However I'm not 100% sure what was the solution. In my last maintenance I did: 1) replaced all lambdas (although they were new installed by shop) 2) found and fix a small (like toothpick) leak in exhaust ~20cm after downstream lambda 3) connected ISTA-P which updated DME (however to the same version as it was before, done by winkfp) Car is like new now. Now the learning fuel trims process works. The car has more power, is smoother and more smoother every driving session (as it learns) and idle is also smooth. Quite happy that this is over Thanks for all suggestions.
	Appreciate 2 The Nightman1090.00 Noir883.00 Quote

01-27-2022, 03:40 PM	#29
SvenHz New Member 6 Rep 24 Posts Drives: 2011 318i E90 LCI Join Date: May 2016 Location: Amsterdam, Netherlands iTrader: (0)	Well done! Are your Learnbits okay if you look in Inpa? Also for the long term, check for error messages periodically. Especially the NOx system is sensitive.
	Appreciate 0 Quote

04-25-2022, 05:20 PM	#31
NiBe First Lieutenant 452 Rep 364 Posts Drives: BMW E91 & E92 Join Date: Nov 2021 Location: Europe iTrader: (0)	To complete the story. The problem reappeared after approx 3 months. I did contact Bimmerprofs again and after few INPA recording he told me that I have leak in exhaust and referenced this his article: https://bimmerprofs.com/n52b30-probl...ulating-probe/ And he was right. I was able to confirm a small leak in exhaust. In my "fix" 3 months ago I already fixed one leak of exhaust but apparently not properly so this time I changed the flexpipe completely and it changed everything. It was quite difficult to confirm the leak as it was very small. I tried soapy water method - nothing, smoking into exhaust - nothing. What helped me at the end was a vacuum cleaner connected to tail pipe and at the same time smoking around the exhaust around suspicious areas and looking if the smoke is sucked into the exhaust. In my case smoke has been sucked via flexible part of my flex pipe. Not much but it was apparently enough the confuse DME resp. postcat O2 sensor that the air/fuel mix is lean resulting in a too rich mixture (spark plugs black) and other problems as described in the thread. Btw after the fix my MPG increased by 10%. Very glad that Bimmerprofs helped me he really knows what he is doing.
	Appreciate 4 Noir883.00 avocet251.50 Phil325i614.50 ornicar134.50 Quote