14.85 AFR, fuel trims pinned at -.16, knock retard?!

This is my first post here so I apologize if I mess anything up!

(For reference, currently have a jbr stage 2 powerpath intake/turbo inlet, turbosmart 50/50 set to full recirc, corksport hpfp internals, jbr rear motor mount, and a catback exhaust on the car. During the time of the first 3 logs, I was on a stratified e tune. I have since reset it to stage 0 to test both.)

When I was doing my maf cal log I noticed some bizarre issues. My fuel trims, short and long term, are all stuck entirely at -.16 and never change, as well as my AFR being pinned at 14.85. The AFR will occasionally jump to 29.25 when coasting in gear, off throttle. What could be causing this? My original guess was a bad upstream o2 sensor, but I can't be certain with my limited experience.

The other thing, something that scares me more. The other day I was accelerating onto the highway, partial throttle, and around 4500 rpm received a 1.89 knock retard. Later that night to test what was going on, I gave it near pedal to the floor and got a mid 4's knock reading for less than a second, where it then sharply dropped off. This was not felt or heard. Later that same night, I did some brief 4th gear highway acceleration at about 70 on the throttle position, 0 knock retard, car ran great! (I should add, although I wasn't logging, prior to the rmm install at WOT I never saw any knock retard. I also got gas from a station yesterday I wasn't familiar with, if that matters at all.)

The next day I reset the car to the stage 0 tune and got some more logs. In town crusing/normal acceleration had 14.85 pinned afr and -.16 stft/ltft just like the stratified map. Highway crusing was the same deal. I did a 2nd gear pull at WOT and received negligible knock retard, boost was limited as it should be, no issues. AFR and stft/ltft still stayed stuck, no change.

I have absolutely no clue what exactly is happening here but it's spooked me enough to stop lurking and to make a post. I have all the log files attached and labeled as mentioned in the post. I'm not going to be driving the car for the time being until I can get this all figured out.

Any help at all is entirely appreciated and valued greatly by my fiancé and I. Thank you all

EDIT: There was slight knock retard on this tune during the maf cal log. I didn't notice this before. I apologize for the logs length as well, my tuner asked for multiple runs on one log

 

Fuel trims at -16 means you have a leak, changing maps won't change that also could probably make your Afr off.

Time to look for that leak, start by checking all the hoses in the engine bay, given the negative fuel trims it's probably somewhere between the turbo and throttle body, or even intake manifold. If your injector seals are old and leaking they could contribute to fuel trims and would certainly explain poor Afr

"Pre-turbo = + trims, air added or sucked in
turbo to TP = - trims, air lost or pushed out
post TP = + trims, air added or sucked in

+5 or -5 is ideal
+7 or - 7 not crazy might want to look into it
+10 or -10 look into it , you got a leak
+20 or -20 shits broke yo"

 

I appreciate all that! Question, with the AFR's and fuel trims never changing, doesn't that indicate a busted sensor of some sort on top of a leak?


Also, I might be totally wrong on this, but are -.16 and -16 fuel trims the same? I currently have -.16 and not a solid number.

 

Bad ENG BAR fuse or O2 sensor. Keep driving on that “spiritedly” and you will likely blow your engine.


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Oh shit I didn't see the decimal yes 16 vs 0.16 are very different! 0.16 would be basically perfect. AFR not moving at all could certainly be the primary (upstream) o2 sensor, replace with OEM only (NTK iirc)

Check the fuses, clean MAF sensor as well.

I'm also on my phone and haven't looked at logs yet

 

If your AFR is stuck at 14.85 you have a bad primary o2 sensor. It is the most important sensor in your car, change it as soon as possible. Also do not drive your car until it is changed, the ecu has no idea what your afr really is, and does no compensation, that's why your stft and ltft are not changing.

Tapatalkkal küldve az én KB2003 eszközömről

 

Thank you! I was on track to do this exact thing. No interest in zzb.

Will do, that's a plan! Thank you!

Which engine bar fuse should be replaced? Or should I just replace all of them since fuses are cheap and engines are not?

 

The bad one — likely ENG BAR 3. Visibly inspect all of them, test them if you can’t visibly see if one is bad, if they are all good then you have an O2 sensor to order.


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Huh. I replaced the sensor with an NGK (NTK) sensor and replaced the eng bar 3 fuse just to be safe. No change. Probably going to take this to a shop and see what they can find afterall.

 

Ok, so just for clarification… step 1 is INSPECT and TEST things, not throw money at it and put in new parts you don’t need and see what happens. Both ENG BAR 3 and 4 are O2 sensor fuses, the wiring could also be shorted from touching hot exhaust pipes and melting the plastic sheath, etc. If you’re not up for the task of diagnostics, I would suggest you always just bring your car to a shop in the first place.


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I had tested the prior o2 and it was in fact bad, and I did have some extra 10 amps laying around for the fuses so I wasn't concerned on changing those.

Turns out changing out the o2 did fix it. My accessport didn't want to read right until resetting the ecu, and then the problem is solved. Thank you for your help.

 

Glad you figured it out.


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I have a related issue, figured id bump the thread because mines similar. When i let off the throttle, my stft go up to around -20, but then level back off to around +0.16/-0.16. My AFR will hold steady at idle at around 14.55-14.85, however again when i let off the throttle, it will creep up to 15.58, seen it go to 16.02 but then pretty quickly level back off to normal. Thoughts?

 

That’s not a similar issue at all. That’s a leak. 14.7 is stoich, which is “perfect” AFR and where you should be any time your foot isn’t on the throttle. If your AFR is hitting 16.02 when you press the throttle, that is lean. That means you have too much air and you WILL blow your engine if you don’t get that fixed ASAP.


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