|Originally posted by yellow fever:|
Will it running rich while cruising affect what it commands at pe. I'm still working on the maf tables.
If your MAF tune is off and the fuel trims are consistently running in the negatives during cruising operation AND they reset to 0% while in PE, then yes, that will cause it to run rich while in PE.
However, if the long term fuel trim is freezing negative when you go into PE, then that fuel trim is being applied while in PE mode. This doesn't mean you don't still have a MAF tuning issue however.
In any case, if you are seeing grossly negative fuel trim numbers while in normal closed loop operation, I would say you need to do some MAF calibration table work to get those numbers as close to 0% as you can. Doesn't need to be perfect (+/- 5% or so isn't bad at all). Remember, you need to combine both Short and Long Term Fuel Trims numbers to get the total amount of trim the PCM is adding or subtracting for fuel from the tune to satisfy stoich (14.7:1 AFR) while in normal closed loop mode.
What I do to tune MAF (in normal closed loop operation) is log these data PIDs:
MAF (hz or gm/sec)
If say @ 2500 MAF hz you are seeing STFT of -4% and LTFT of -6% (-10% total); to correct this, reduce the MAF flow (gm/sec) @ the 2500hz slot in the MAF cal table by 10%. Make sure you smooth the values above and below where you make changes so there aren't any spikes in your MAF calibration table when you are done.
Once the system goes into PE mode the fuel trims should either freeze or reset which means you need to look at your Wideband O2 data to determine what changes need to be made at that particular MAF flow range. Compare actual Wideband O2 AFR with scan data commanded AFR and adjust MAF flow gm/sec in that operational area to correct the discrepancy.