on April 21, 2009, 10:57 am, in reply to "Vauxhall Corsa 1.0 2002 - MIL on and code P0170, fuel trim #"
Fuel trim codes are probably one of the worst to diagnose as they have so many contributory factors.
Last November I had a Kia Sportage code P0171 but with no running problems including hard accel up a steep bank,ruling out the MAF.
I did most of the normal checks having noted that the STFT & LTFT were +25.I cleared the code. Having the use of a CRecorder I was able to recognize on the grathing section downloaded to computer that the fuel trims were normal at cruise +-5% but climbed at idle.
This ruled out fuel pressure/injectors etc.
I had spent some time trying to locate what I believed to be a vacuum leak.
I tried again more thoroughly using a propane canister and long tube around the inlet manifold PCV & all vacuum take offs whilst connected to my gas analyser. Then I found it a vac take-off at the rear of the manifold out of sight had lost its cap. There had been no suction noise and the vehicle had no problem recently on MOT emissions.
Hope this helps
Dek
