Bank1 unstable fuel trim

Jhill

Did you do any kind of mechanical engine checks? Compression, leak down? Sounds like you’ve done all the control side stuff swapping but you say it’s happening after an engine swap. What’s the condition of the engine? If your having a bad or weak cylinder it’s going to show more at idle than at higher RPM. I’d suspect it to have to be pretty bad to throw off the fuel trims that much and would show more running condition issues (misfire etc) but as you’ve already done all the injectors which would be the only other main thing aside from a shorted harness which again should massively show an issue.

projectpanda

I haven't done a compression or leak down test. I can do a compression test next, just to confirm. The engine is a low mileage engine I got locally, 15,000 miles from a reputable shop, so I didn't think about a weak cylinder at first.

I forgot to mention, I swapped the O2 sensor (upstream) and the fuel trim seems to not be as erratic, bank1 in the 90s-100, and bank2 80s-90s.
O2 sensors were new when i installed them.

__________________
RHM 75mm TB & ported up/low mani., 3" intakes/velocity stack, Z1 Headers, Motordyne ART pipes, HBP 3.5" exhaust, Tein MonoSport, SPL F/R arms, endlinks, and tie rods , Eibach sways, Z1 rotors F/R, diff bush., subframe collar, Bell Raceworks diff brace