I have a 4 cylinder 2005 Accord with a high STFT of 45%. The problem reports as a P0171. Despite the high STFT, the car starts and performs normally.
I hope someone can give me some advice.
I have done the following without making the STFT go away:
1 I have replaced the fuel pump and fuel filter and had the injectors professionally cleaned. Fuel pressure is 50 psi.
2 I've replaced both O2 sensors.
3 I have swapped the MAF sensor with a known good one.
4 I found one vacuum leak in the Front Engine mount and replaced it.
5 I've blocked off/ plugged all the vacuum lines, ie the brake booster line, the purge line, the PCV hose line.
6 The MAP sensor reads 4.5 psi at idle and 3.6 psi at 3000 rpm. Is that correct?
7 I don't think there any intake manifold gasket leaks. I've used starting fluid in the area. There are no fuel injector seal vacuum leaks, which happened to me on another car.
Can someone give me guidance on what to check next?