Originally Posted by Jeffman
I'm not sure where you heard that but in my experience it is correct. My short and long term fuel trims began diverging around 3k or so, and grew apart until they were something like +34% and -32%. I drove it like that for a long time and it showed no sign of correcting. I even replaced my lpfp in there with the walbro 455 (fuel pressure is great now) and that didn't do ANYTHING to my fuel trim issue.
I think once it gets beyond a certain point the ECU logic doesn't allow it to correct itself. People said I needed to fix my fuel scalar
, but that was not correct; the fuel scalar was spot on. It was the learning that was jacked up. I reset a bunch of things (took a couple trys, as stated before... picky car) and not only did my fuel trims zero out, but 1000 miles afterwards my stft and ltft for both banks are within a couple points of each other, and +/- a few points as well.
As an aside, my 50/50 E85/ACN91 gas mileage went from ~14-16 to 20+. "