Question about GMC Sierra 1500

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I have a 2002 GMC 4x4 Sierra 1500 5.3L - After starting in the mornings, the engine revs up and then idles very low almost to the point of dying sounding very rough. Runs fine after it warms up. I have replaced the air filter and mass air flow sensor, fuel pump and filter, fuel pressure regulator, plugs and plug wires. Seemed a little better after replacing the fuel pressure regulator. Some say to replace the IAC or the air intake gasket. All codes say misfire.

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  • tedge1988 Feb 09, 2010

    Check engine light is on. It only revs up high after starting in the mornings. It went off for 2 days and came back on flashing while in the car wash.

  • tedge1988 Feb 10, 2010

    The codes are PO171, PO174 and PO300.



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Is the check engine light on? Does it only rev one then go low or keep reving up and down? Thanks

Posted on Feb 08, 2010

  • edwin187 Feb 09, 2010

    Ok, bring the vehicle to your local parts store and have them connect a scantool to check the diagnostic codes and let me know what codes your getting. Thanks



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