why does my chevy astro idle high?

1998 CHEVROLET AVALANCHE
135,000 MILES
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HELPLESSASTRO
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I replaced intake manifold gasket and did not remove throtle body from manifold. Put new gasket on plug every thing back in and now idles like i got my foot on the pedal all the way down. Please someone help.
Nov 13, 2011 at 1:23 AM
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JACOBANDNICKOLAS
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Have you checked the idle air control valve? Also, check to make sure the TB doesn't have a vacuum leak.
Nov 13, 2011 at 2:00 AM
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HELPLESSASTRO
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where is the IAC located and how do I check it.
Nov 13, 2011 at 3:46 AM
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JACOBANDNICKOLAS
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  • 110,194 POSTS
  • ASE Certified Mechanic
It is located on the throttle body. Remove it and you will see a pintil valve at the end of it. That valve is what allows air to enter the engine when the throttle plate is closed so the engine can run. If adjusts in and out to maintain idle based on info from the computer. Once it is out, have a helper turn the key on and off. It should move. If it doesn't, it's bad. Also, make sure there is no carbon build up on it.
Nov 13, 2011 at 3:51 AM
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JJIMENEZ8891
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Agreed also make sure that the gasket to intake sealed correctly so that you dont have a leak their either.
Nov 13, 2011 at 4:13 AM
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HELPLESSASTRO
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IAC works and is clean throttle stays open how do i get it to close.
Nov 13, 2011 at 8:10 PM
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