GM Truck/Chev Avalanche 5.3L rough idle question

Discussion in 'The "Other" Bench' started by goof, Nov 15, 2009.

  1. goof

    goof Well-Known Member

    I have an '02 Chevy Avalanche with 140K on it. I bought it about 4 months ago and it has always run just fine. Now that the weather has gotten cooler, it stumbles and surges during warm up when it is cooler than about 50 degrees outside. It acts like an old car with a carb and no choke! It runs (idles) rough until it gets to operating temp and then it is just fine. Anybody got any ideas:Do No:
     
  2. Billhillytim

    Billhillytim Well-Known Member

    As crazy as it sounds, never rule out the fuel pump, especially if it is getting poor gas mileage. My electric one failed on me in the 2007 Avalanche, and it took me several minutes to get it started, when it did, it stumbled a bunch and the only indication it was failing was the intermittant check engine light with a code stating lean on banks one and two. Definitely run a scanner on it from your local parts store to see if there was a code that popped up and just went off on its own. GM uses an extremely high amount of fuel pressure and with the slightest drop conditions like this occur.
     
  3. Steve A

    Steve A 454 450

    I'm guessing that it's the idle air control valve.
     
  4. TORQUED455

    TORQUED455 Well-Known Member

    More than likely the intake manofold gaskets are leaking. I have replaced many for your exact symptoms. Very hard to smoke test, etc.
     
  5. Sir Speedy

    Sir Speedy Well-Known Member

    X2. Try spraying carb cleaner around the intake gaskets and see if the rpm changes. If it does the gaskets are leaking. What happens is the seal shrinks on the gasket when cold and expands when hot. GM has improved the replacement gasket with a more robust seal, so I recommend getting a GM gasket kit. Usually a weak fuel pump will cause extended cranking time.
     
  6. idahoskylark

    idahoskylark idahoskylark

    running cold water over the manifold will show a leak before carb clean will have found many leakers this way
     

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