2002 Chevy Silverado engine idles rough in cold

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Engine Performance problem
2002 Chevy Silverado 6 cyl Four Wheel Drive Automatic 130000 miles

I have had the problem for several years now and have just been living with it. It only does this when it gets cold out. Below 50 mainly. When you first crank it up it idles up real high for a few seconds then idles back down and just kinda lopes and will barely run. Once you get the engine warmed up it gets better and once the temperature is up to 200 it runs perfect. I have had a coolant temp sensor and idle air control valve replaced and still no help. Thanks

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Wednesday, January 14th, 2009 AT 12:23 PM

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Check the intake for leaks, follow this info: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. The technician may also notice lower than normal MAF readings if the intake seals are leaking.

If leaking intake gasket seals are found, replace the intake gaskets. During the repair be sure to use the current GMSPO part number for replacement intake gaskets. The current GMSPO part number for intake gaskets will have a teal green intake gasket seal. 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. Service Information states, "An intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area should be replaced". Intake warpage is measured at the gasket sealing surfaces, and should be measured within a 200 mm (7.87 in) area. This measurement is across only two of the intake runner port openings. Measurements taken across the entire distance of all four intake runner ports will lead to unnecessary manifold replacements.
See if this works, post back if it doesn't and will advise.

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Wednesday, January 14th, 2009 AT 12:29 PM

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