AFR Command Fluctuations

[steve99]

Originally Posted by NicFromTheNorth

Unfortunately for now I can't disable the A/F#3 tables because they are not defined in OFTv4_ZA1JF00C.xml . Until I find a workaround and update my rom I will log open-loop runs as suggested by @solidONE to check that everything is normal at high loads. I had not done it yet because I was driving cautiously just in case my car indeed had an issue.

#af3 can cause issues manily due to a lot of headers put the rear 02 sensor in a long tube and sensor doesnt sit ig gass flow so it reads incorrectly, like whwn using an 02 spacer in rear 02, but lot of headers have a similar spacer.



they are not defined in the supplied oft tables


but if you use the ones linked below they have #af3 tavles defined




https://www.ft86club.com/forums/showthread.php?t=126180

[NicFromTheNorth]

This is quite after the fact as the summer was a busy one.
I was able to attenuate the lean AFR pockets I observed previously by doing this:
1) putting more voltage reference points in the 3-4V range of the MAF Sensor Scaling table and rescaling the MAF,
2) modifying the Engine Load Compensation table.
I did a few 2nd gear pulls and the results are shown in this graph. AFR is still not perfect but good enough to my liking. The engine loads on the other hand tell me that the AVCS tables need improvement.

[solidONE]

I started to get some pretty wild fluctuations in my commanded AFR and AFR after reverting back to factory, then reinstalling long tube header. Switching out the O2 sensor doesn't seem to effect it. It would still have these fluctuations even with brand new O2 sensors.



This behavior seems to effect the idle as well at times, causing the rpm to dip and engine to cut off. What would cause the commanded AFR behave this way if it was not a faulty O2 sensor? Misfires? Exhaust leak at the headers? Has anyone seen this kind of thing before?



https://datazap.me/u/solidone/afr-fl...8076&mark=7744




https://datazap.me/u/solidone/afr-fl...7616&mark=7744

[tomm.brz]

Originally Posted by solidONE

I started to get some pretty wild fluctuations in my commanded AFR and AFR after reverting back to factory, then reinstalling long tube header. Switching out the O2 sensor doesn't seem to effect it. It would still have these fluctuations even with brand new O2 sensors.



This behavior seems to effect the idle as well at times, causing the rpm to dip and engine to cut off. What would cause the commanded AFR behave this way if it was not a faulty O2 sensor? Misfires? Exhaust leak at the headers? Has anyone seen this kind of thing before?



https://datazap.me/u/solidone/afr-fl...8076&mark=7744




https://datazap.me/u/solidone/afr-fl...7616&mark=7744

disable the useless secondary o2 sensor by zero'ing the 2 af#3 tables

[solidONE]

Originally Posted by tomm.brz

disable the useless secondary o2 sensor by zero'ing the 2 af#3 tables

The thing is, I think this was happening even with a complete revert to stock including the original factory tune. Something is definitely not working normally. I was hoping it was the downstream O2 when I couldn't find a vacuum or exhaust leak, but unfortunately it behaved relatively the same when I swapped it out.



I suppose I can give that a try and see if it changes anything.

[solidONE]

I zeroed out the AF #3 limits (CL Target compensation Limits, Correction Limits, Learning Limits), the idle no longer dips and I havent had the engine cut off coming to a stop, but I still have this odd condition where the commanded afr hangs at 15.06 during part throttle operation. It seems to happen mostly right when the engine load comes to 0.8. Before the load hits 0.8 or as soon as it goes past 0.9-1.0 engine loads, the commanded afr seems to work fine. Very strange. I'm still suspecting an exhaust leak (header gasket or small crack in headers?), but I'm not so sure that would explain the behavior in commanded AFR?



https://datazap.me/u/solidone/log-16...3888-8330-8346

[solidONE]

Originally Posted by solidONE

I zeroed out the AF #3 limits (CL Target compensation Limits, Correction Limits, Learning Limits), the idle no longer dips and I havent had the engine cut off coming to a stop, but I still have this odd condition where the commanded afr hangs at 15.06 during part throttle operation. It seems to happen mostly right when the engine load comes to 0.8. Before the load hits 0.8 or as soon as it goes past 0.9-1.0 engine loads, the commanded afr seems to work fine. Very strange. I'm still suspecting an exhaust leak (header gasket or small crack in headers?), but I'm not so sure that would explain the behavior in commanded AFR?



https://datazap.me/u/solidone/log-16...3888-8330-8346

Spoke too soon... stalled three times in a row coming to a stop. Then three time the idle dipped (progressively less prodounced), then back to normal again...


https://datazap.me/u/solidone/stall-...3370-4828-5854


@steve99 @Kodename47 you all have any idea?

[steve99]

Originally Posted by solidONE

Spoke too soon... stalled three times in a row coming to a stop. Then three time the idle dipped (progressively less prodounced), then back to normal again...


https://datazap.me/u/solidone/stall-...3370-4828-5854


@steve99 @KOdeneame47 you all have any idea?

Increase the values in the overun fuel resume tables say 200 rpm at the bottom end

[solidONE]

Originally Posted by steve99

Increase the values in the overun fuel resume tables say 200 rpm at the bottom end

I will try that, but its doing the same thing with completely oem hardware and the original factory A01C rom.


This issue popped up right after I reverted back to stock for smog check, and stayed this way after reverting back to the previous setup minus the flex fuel. I did not reinstall the oil cooler or flex fuel system. With the long tube header, with this tune the closed loop fueling was pretty dead on, but now it run rich into the 11's:1 afr going high and wide open throttle. As well as this dip and stalling and the commanded afr issue. Same exact intake and exhaust set up.

[waltco]

Hey @solidONE, did you resolve this?

I am noticing that AFRs are doing something similar cruising at lower loads:

https://datazap.me/u/cjwalther/16nov...4-6&zoom=5-583

I'm also A01C, running stock intake, but just threw on a ptuning 4-1.

[x808drifter]

Originally Posted by waltco

Hey @solidONE, did you resolve this?

I am noticing that AFRs are doing something similar cruising at lower loads:

https://datazap.me/u/cjwalther/16nov...4-6&zoom=5-583

I'm also A01C, running stock intake, but just threw on a ptuning 4-1.

Last post was from last year.
Last Activity: 09-24-2021 01:09 PM


Go to someone in here that's still active.

[tomm.brz]

did u try zero'ing af#3 trims?