Quote:
Originally Posted by andrewwynn
Have you measured fuel psi yet? If it's over 50 FPR is shot and will cause rich mix and negative trims.
The MAF can send incorrect value to cause a similar problem also but I thought i saw you tried a couple different ones.
–awr–
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No, I haven't yet found the adapter I bought to fit the Schrader on the fuel rail. If I don't find it tomorrow, i'll order another.
Years ago, on 5-11-2022, when I measured pressure, it was
barely at minimum, IIRC. But, i didn't have misfires, hard starts, or long crank times, and only had the mysterious lean fuel trims (that everyone assured me was a vacuum leak...never found one).
Now, with a new fuel pump, and suddenly running super-rich, it doesn't look like a vacuum leak anymore.
What sort of fuel pressure would cause those fuel trims I'm now getting? and the surges of power, and/or the stumble/stall/limp mode following those 90 degree curves?
After using cheap $20 MAFs to combat erroneous fuel trim numbers (trying anything to do a workaround, since I never found the root cause of the lean trims),
X5chemist showed pity for me and offered a proven-good, OEM Siemens-VDO MAF for me to use, at least until i could find the true cause of my lean fuel trims.
the Siemens-VDO MAF was giving me fuel trims that were much more normal, and I was quite happy with those numbers, and had thought that perhaps it wasn't a MAF problem, or even a vacuum problem, but maybe an injector problem (but why in both banks, with injectors only <5k miles old?), and I was using more and stronger fuel system and cat cleaning additives to try and fix the flow; I should've reasoned that the fuel system further upstream was the culprit.