'01 540i fuel trim problems
I'm new here and was wondering if you can help.
I have been experience lumpy idle when cold and cutting out when first started. I've re-tightened the inlet manifold which has helped a lot (no more cutting out). I've checked for vacuum leaks around the intake; O2 sensors are less than 1 year old, maf sensor is new.
I've plugged in a hand-held OBD-II reader to to monitor short and long term fuel trims and get the following:
Took the car for a long run (80+ miles and got):
STFT Bank 1 - 000% -> perfect
STFT Bank 3 - 008% -> bit high, see LTFT
LTFT Bank 1 - 003% -> perfect!
LTFT Bank 3 - 012% -> worrying
STFT Bank 2 - 008% -> bit high, but LTFT is ok!
STFT Bank 4 - 010% -> very worrying, see LTFT
LTFT Bank 2 - 000% -> perfect!
LTFT Bank 4 - 010% -> worrying.
Then took the car, next day, for a short run (3 miles):
STFT Bank 1 - 003% -> not bad but increasing, see LTFT
STFT Bank 3 - 010% -> bit high, see LTFT
LTFT Bank 1 - 007% -> increasing
LTFT Bank 3 - 017% -> worrying
STFT Bank 2 - 000% -> perfect
STFT Bank 4 - 007% -> very worrying, see LTFT
LTFT Bank 2 - 004% -> not bad
LTFT Bank 4 - 015% -> worrying.
I've also discovered that Bank 1, Sensor 1 and Bank 2, Sensor 1 are PRE-CAT. Sensors 2 on both banks are POST-CAT.
So problems on bank 3 and 4, wherever they are.. but I think it basically means pre-O2 sensor adjustment it is running lean (too much air).. what do you reckon?