Technical LOG REVIEW: Weird AFR Bank Issue

[suspenceful]

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

 

[Dreyo27]

Pull your injectors, bet you one is going to be a different color compered to the rest.

 

[suspenceful]

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.

 

[Rob09msport]

Def gonna be an injector not o2 sensor and probably a pi

 

[chadillac2000]

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]

Def gonna be an injector not o2 sensor and probably a pi

This .....but can u upload a csv. ?

 

[nahor]

This .....but can u upload a csv. ?

You can download csvs directly from Datazap, the button is towards the bottom right.

 

[SlowE93]

Cant seem to do it on my phone

 

[nahor]

Cant seem to do it on my phone

Does your browser have a request desktop site option? It shows up on mine as long as I check that.

 

[SlowE93]

Ahhh.....didnt try that.....lemme see

 

[SlowE93]

I dont believe it to be pi looking at the logs now. I would start with O2s

 

[Rob09msport]

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]

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.

 

[suspenceful]

I swapped O2 sensors across banks this weekend, but no change. Still wacky AFR in bank 1.

https://datazap.me/u/suspenceful/weird-afr-o2-swapped?log=0&data=1-4-14-18-24-35

What should I check for now?

PS: I attached all three logs CSVs.

 

[Rob09msport]

Could pcv affect that ?

 

[tan_rich]

Do you have a log of your ltft? Also get a log of you cruising at 50-60mph.

Mileage on car?

 

[suspenceful]

Do you have a log of your ltft? Also get a log of you cruising at 50-60mph.

Mileage on car?

Not sure what ltft is. I can try to get a log while cruising soon. Engine has ~90k.

 

[LoBoost]

long term fuel trim?

 

[tan_rich]

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]

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.