Long-term fuel trims in the high teens. Ignore it or fix it?

Discussion in 'General Chevy & GM Tech Questions' started by Jamm3r, Feb 28, 2014.

  1. Jamm3r

    Jamm3r Member 2 Years 100 Posts

    I have a 1997 K2500 with a 5.7l fuel injected engine.

    The truck has never run quite right as long as I've owned it. Recently replaced the fuel pressure regulator, which was leaking, which helped a great deal. Also recently replaced the MAF sensor which worked OK most of the time but went off in the weeds once in a while, then the trims would peg at 25 and the MIL would go on.

    Truck runs much better than before but long term fuel trims are still +15 to +18 at idle and +8 to +12 at highway cruise. Trims are within 3% between left and right banks.

    Recently replaced the fuel pump because it had failed, new pump is ACDelco$$$, pressures now around 50-55 PSI while running. No effect on trims

    I have checked for vacuum leaks and can't find anything. I've pinched off the evap and brake booster hoses, no change. Waved an unlit propane torch around the plenum, manifold, and throttle body, no effect.

    O2 sensors are a couple of years old and no reason to think they should be bad by now.

    I'm not sure what to do with this. Truck runs OK now but the received wisdom is that the trims really should be in the single digits. Truck has 98,000 miles on it and am hoping to get 98,000 more.

    Any advice or insight welcome

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