Mechanics

CHEVY CHECK ENGINE LIGHT

2002 Chevrolet Tahoe

Engine Performance problem
2002 Chevy Tahoe V8 Four Wheel Drive Automatic 105000 miles

check engine light come on and off sproadically. Engine idles @ 500 rpm very roughly when in drive but otherwise runs smooth at speed. Happens when in drive when at stop with brakes applied. Seems to surge and buck. Codes that come up on diagnostic are 171 and 174, lean left and right bank. First check was to check and clean MAF sensor. After that codes suggest oxygen sensor or possibly fuel pressure regulator. Engine runs smooth after reaching operating temp.
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Dtschro
December 29, 2009.



Check for a vacuum leak around the upper intake manifold, very common for these to leak, 99 through 05 GEN III truck engines may experience any of the following: A cold rough idle that diminishes as the engine warms up.
Possible DTCS P0171, P0174, or P0300.
Random misfires at idle. The intake gasket seals may be leaking around the intake ports, causing a lean condition. The intake gasket seals may leak around the bottom side of the port, making it a challenge to detect the vacuum leak. If leaking intake gasket seals are found, replace the intake gaskets. The old version of the intake gaskets were orange in color. Use only the teal green colored gaskets for a repair. The intake plenum should also be checked for excessive warpage that may cause an uneven clamping pressure of the seal. If the plenum is found to be warped it will need to be replaced.

Brian 1
Dec 30, 2009.