P0300 only at idle what could I be missing

Asked by Josh Mar 27, 2022 at 06:12 PM about the 2004 Chevrolet Avalanche 1500 4WD

Question type: Maintenance & Repair

I've put new coils plugs wires throttle body crank shaft
position sensor cam sensor purge vavle fuel pump and
had injectors clean idk what else it can be it driving me
crazy it's has 300,000 on it but runs fine only get code
at idle buy goes off while driving  help help help

4 Answers

Josh answered 2 years ago

No vacuum leaks I can find either haven't done compression check yet just trying get figure out what else to do

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Gene answered 2 years ago

I had this happen on a Tahoe I owned, anyway long story short it turned out to be leaking lower intake manifold gaskets.

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james answered 2 years ago

Intake manifold vacuum is highest at idle then drops as you accelerate. An intake manifold vacuum leak makes sense. Hope that helps! Jim

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