Technical LOG REVIEW: Weird AFR Bank Issue

suspenceful

700 HP Club (N54)
Aug 1, 2017
542
551
0
Ride
2015 M3, 2008 135i, 2009 335i
Today I was doing some 3rd gear pulls and noticed at the top of the RPM range I would feel a noticeable hesitate and let off. After looking at the logs, I'm noticing that my AFR bank 1 shoots up to 20 (max) while AFR bank 2 stays at ~12.

Why would this be happening? Bank 1 primary sensor going out? Bank 1 injector(s) (DI or PI) not firing properly? Started happening out of the blue. No check engine light or codes. I don't really want to gamble with weird stuff happening at this power level. Hoping someone sees something I don't in these logs.

https://datazap.me/u/suspenceful/weird-afr-v1?log=0&data=1-4-18-24

https://datazap.me/u/suspenceful/weird-afr-v2?log=0&data=1-4-18-24
 

suspenceful

700 HP Club (N54)
Aug 1, 2017
542
551
0
Ride
2015 M3, 2008 135i, 2009 335i
Pull your injectors, bet you one is going to be a different color compered to the rest.

The direct injectors? I think I'll swap O2 sensors first and see if the problem follows banks.
 

chadillac2000

Corporal
Oct 26, 2017
233
254
0
NC
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2008 BMW 135i
I'm not used to using Datazap, but looks like your trims are all over the place. They max out as you get into boost before dropping to to 0 as you get into the meat of the power-band, then bank 1 vs bank 2 trims start to separate, before it eventually hops into open loop fueling. As you said, not good when at WOT.

Have you allowed the car to sit with the ignition on, but not started, so the JB4 can lambda adaptions can be reset? Over time, not allowing the lambda adaptions to reset can cause trims to separate and they can start causing problems.

I think you're on the right track with the o2 sensors, but as others have said, could easily be a PI injector issue as well.
 

SlowE93

Lieutenant
Jul 2, 2017
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E93
I dont believe it to be pi looking at the logs now. I would start with O2s
 

Rob09msport

Major
Oct 28, 2017
1,928
662
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Monroe CT
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09 335i msport le mans 18 x5
I didnt look at logs but was going off of the description, question though If you shut off pi and load a stock boost or no boost map how does everything look that could be quick way to start ruling things out.
 

SlowE93

Lieutenant
Jul 2, 2017
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E93
Trims bank 1 and 2 follow each other in the log I looked at, so thats what leads me to believe it not a fueling issue. When pi injectors or di begin to fail, its usually apparent in stft. There will be a variance from bank to bank. Trims maxed out will cause a lean condition which in his case, trims appear to be in check.
 

tan_rich

Specialist
Feb 6, 2018
89
18
0
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335is
Do you have a log of your ltft? Also get a log of you cruising at 50-60mph.

Mileage on car?
 

tan_rich

Specialist
Feb 6, 2018
89
18
0
Ride
335is
Not sure what ltft is. I can try to get a log while cruising soon. Engine has ~90k.

long term fuel trim?

Yes long term fuel trim, I’m not too familiar with the jb4 descriptions but in MHD there is LTFT. You should check those to see if they are acting irregularly as well.

The secondary o2 sensors in our cars play a part in the fuel trim of our cars. They can affect the ltft which in turn affect your stft. 90k miles seems a like a good time to replace your o2 sensors, pre and post cat ones.
 

suspenceful

700 HP Club (N54)
Aug 1, 2017
542
551
0
Ride
2015 M3, 2008 135i, 2009 335i
Yes long term fuel trim, I’m not too familiar with the jb4 descriptions but in MHD there is LTFT. You should check those to see if they are acting irregularly as well.

The secondary o2 sensors in our cars play a part in the fuel trim of our cars. They can affect the ltft which in turn affect your stft. 90k miles seems a like a good time to replace your o2 sensors, pre and post cat ones.

Gotcha - I don't think JB4 reports that in logs.

The primary and secondary O2 sensors all have less than 3k miles on them.