Unexpected Fuel Trim behavior

[Andy0x1]

OK,

Failed MAF (0Hz)

Disabled and reset Trims

Tuned VE table +/- 1% Via Wideband.

Re-enabled MAF

Changed RPM threshold from 2500 to 0

Tuned MAF +/- 1% Via Wideband.

Re-enabled TRIMS, CL, and returned threshold to 2500

and now further logging shows trims in play again...

is this to be expected?

Should I be 0'ing out the MAF g/sec table in addition to setting the fail Hz 0 when tuning the VE?

(MAF was not logged while tuning. it.)

[CarsonTech]

If you set the MAF Fail High to 0 and you are getting the P0103 DTC fail and SES light, the MAF should be failed. You can check by zeroing out the MAF table, but the MAF should be failed after setting MAF Fail High to 0.

I have never had to zero out the MAF table, I just read about doing this just to check to make sure the MAF is failed.

[5_Liter_Eater]

If you re-enabled closed loop then fuel trims will be in play again. Nothing unexpected about that. They should be closer to zero than pre-tune. If you have LTFTs enabled then don't even look at STFTs.

[Andy0x1]

I understand that it's normal for the trims to move around in closed loop, What I'm surprised about is that while tuning; the AFR was within 1% of perfect, yet with Closed Loop and trimming re-enabled, The VCM is correcting on average 3% but as high as 7% in some of the fields...

With the MAF failed, it seems to be close to 1%

Yet when tunning the MAF, that's within 1% as well...

I don't know, maybe it's user error and I'm doing something stupid, I had a late night...

Would it be a bad idea to disable (only) LTFT and use the STFT's to further correct the VE (in closed loop)?

[Twitch]

I understand that it's normal for the trims to move around in closed loop, What I'm surprised about is that while tuning; the AFR was within 1% of perfect, yet with Closed Loop and trimming re-enabled, The VCM is correcting on average 3% but as high as 7% in some of the fields...

With the MAF failed, it seems to be close to 1%

Yet when tunning the MAF, that's within 1% as well...

I don't know, maybe it's user error and I'm doing something stupid, I had a late night...

Would it be a bad idea to disable (only) LTFT and use the STFT's to further correct the VE (in closed loop)?

Same here. I was hoping that, in time, with enough small adjustments, I can get everything close.

[5_Liter_Eater]

You will never get to +-1% in CL even if it was spot on with the wide band. The high error cells are probably where there is a lot of throttle transition. Anyway, I do like to tune the non-PE areas with fuel trims after doing an open loop calibration. The PCM is going to use the trims anyway. I do advocate disabling LTFTs indefinitely and only run with STFTs in closed loop. This way you don't have to worry about positive fuel trims adding to PE. STFTs do not do this, only LTFTs do. So unless your tune is off bt +-25% the STFTs can do a fine job.