long term fuel trim

any one know wht would cause it to be -20.31% this is wht i was told but not sure why the ck engine light isn't on runs well but has aruff idle any one run in o this be for?? its a 02 toyota tacoma 2.7 i have

131000 on it thanks

BAIN15

Reply to
dan baker
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The ECU thinks it is running rich so it is taking away fuel, that is why the long term fuuel trim is -20.31%. It could actually running rich OR it could be caused by a failing O2 sensor. You need to look at the O2 sensor reading to diagnose this problem. The front O2 sensor is the one that controls the A/F mixture.

Reply to
Mike

ok i had the font one replaed bout 3000 miles ago and the back o2 is origeal i think i was told when i got this readding every thing was in range but the long trim so i guess ill have to spend the 120 to have it checked thanks any how

BAIN15

Reply to
dan baker

If you have already had the front O2 sensor replaced then I would have to guess that it is actually running rich. I would suspect a leaking fuel injector. One way can can check this is to hook up a fuel pressure guage and run the engine then shut it down. Leave the guage hooked up for several hours or longer if needed. Watch the guage to see if the pressure drops. You may be able to pull the fuel rail and injectors as an assembly and actually see the fuel leaking from one of the injectors when the fuel rail is pressurized.

Reply to
Mike

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