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What would be the diagnosis for a high idle (1800-2000) constantly?

mrceeiveymrceeivey Member Posts: 1
edited February 2016 in Chevrolet
So I've already replaced the idle control valve but to no avail. I took off the throttle body and cleaned it (much needed) by the way..lol. I also cleaned the mass airflow sensor but still nothing, Has anyone dealt with this before and if so how did you resolve the issue? By the way im dealing with a 1998 Chevy Silverado 1500 305 (V8) 5.0L

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    Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    Could be lots of things. Simple test for starters might be to test for a vacuum leak by spraying some carb cleaner around the throttle body gasket and the intake manifold gasket. If the idle speeds up even further, then you have a vacuum leak--which changes the air/fuel mix and could....could....give you a high idle.

    Also do a computer scan and see if any codes are stored. How about the throttle plate? That could be carbonized.
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