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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > AFR Imbalance (Bank 1/2) - Bad Injector? Logs Attached



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      12-24-2012, 05:59 PM   #1
NiVeDh
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Question AFR Imbalance (Bank 1/2) - Bad Injector? Logs Attached

Wondering if anyone else has experienced anything similar to this.

Bank 1 AFR tends to be richer during transients. Cylinder 3 plug had some black soot, was wet, and smelled like gasoline. No codes. Plugs and coils have <10K miles on them. Intake valves cleaned a couple of weeks ago. Car has 65K miles.

Thanks to Joshboody, jdbretz, dzenno, and themyst for all the help with diagnosing these issues.

We are thinking it's a leaky or defective cylinder 3 injector. Any chance it could be the O2 sensors?

Note: these are not WOT logs. The car was idling and I just jabbed the accelerator for a second or two to bring the RPMs up to ~3K and then let off.







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      12-24-2012, 06:29 PM   #2
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Since you have access to INPA, can you swap cylinder 3 injector to bank 2, recode them, and see if the problem follows? That seems like it may confirm the injector theory.

Didn't you already change your injectors? Do you still have those extra ones sitting in your garage you could use to further test things out?
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      12-24-2012, 10:27 PM   #3
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Quote:
Originally Posted by jdbretz View Post
Since you have access to INPA, can you swap cylinder 3 injector to bank 2, recode them, and see if the problem follows? That seems like it may confirm the injector theory.

Didn't you already change your injectors? Do you still have those extra ones sitting in your garage you could use to further test things out?
Injectors were replaced about a year ago under the recall. I ordered some new ones today. I'll take some more logs in the meantime.

I just took some logs and oddly enough, the AFRs look nice and smooth on the Cobb "stock-like" map but there a lot of overboost-induced throttle closures. I'm guessing the reason is because it's not tweaked for the increased VE of a FBO car. I'll try the more aggressive maps tomorrow.

Sorry, forgot to log boost on these and sorry for the messy plot (RPM is dark blue and on secondary axis).



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      12-24-2012, 11:08 PM   #4
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I think you're right about the overboost conditions on the stock simulation "map 0." I've only seen a few map 0 logs but they all seem to have overboosts that clear up when running maps designed for FBO.
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      12-30-2012, 11:39 AM   #5
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I'm convinced it's an injector. Will do some more diagnosis to figure out which one. Strangely, there are no codes.
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      12-30-2012, 12:43 PM   #6
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I think it's an injector too. I dont think the imbalance is enough to throw a code. Sometimes it throws the mixture code, other time you get a rough idle and misfire at idle.

Swapping injectors 3-4 or 3-2 would be the easiest diagnosis since there are no codes at this juncture.
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      12-30-2012, 04:15 PM   #7
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Am I in the same boat with this issue? My 2nd bank appears to be running lean on many of the logs I have made.

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      12-30-2012, 08:03 PM   #8
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OP I would just change injector #3 since you said the plug was wet and black.

For the log above, graph them separately, rescale, and then AFR banks will match.
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      12-30-2012, 11:16 PM   #9
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Quote:
Originally Posted by Joshboody
OP I would just change injector #3 since you said the plug was wet and black.

For the log above, graph them separately, rescale, and then AFR banks will match.
Replace the Injector
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      02-25-2014, 06:28 PM   #10
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Forgot to update this thread. Turned out to be a missing decoupling element... after a dealer did the injector recall.
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