Question about 1998 GMC Sierra
The normal idle for your engine should be 550 to 600 RPMS so thats not to far off . But the fluctuation is more likely the crank pisition sensor then the EGR valve this engine has a condution called crankshaft wip witch is normal but going down a rough road can somethimes set off a misfire code It wouldn't be a bad idea to take the EGR valve off and clean it and check it but the CPK would give you the fluctuation in RPMS . It still could be a few outer things but this it the most likely cause
Posted on Apr 02, 2011
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Posted on Jan 02, 2017
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