Chevrolet Repair: 98 GMC Sierra 5.7 idle speed., gmc sierra, vavle

Question
I have a 98 GMC Sierra 5.7 V8
It idles at 600 RPM but it seems to either idle to slow or that it's missing cylinders. when im stopped at a stop light I can feel the eingine shaking the truck and sometimes it will kill the engine. The only time im having a problem is when i'm idling because once I give it gass and take off there isnt any problem. Do you think that the problem is the spark plugs or do you think that the idle speed should be turned up. Tanks alot for your time.

Michael

Answer
Idle is completely controlled by the comptuer with the IAC valve and there is no adjustment.  Clean the throttle plates and check ignition timing.  Check and make sure the EGR valve is completely sealing.  A stuck or carboned vavle can cause idle issues.

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