WHY IS MY GMC SIERRA IDLING HIGH WHEN I COME TO A STOP?

  • Tiny
  • tylercovell
  • 2000 GMC Sierra
  • 212,500 miles

I have a 2000 GMC Sierra 1500 5.3 and I recently changed the IAC and the TPS and cleaned the egr and maf sensors and it fixed the problem of rough idling and sputtering. Now after doing all of that sensor work it now feels like the throttle gets stuck when I slow down and come to a complete stop. When I'm at a stop the truck sits at roughly 1200 rpms for at least five seconds and then it will go back to the normal idle. Why would it be doing that?

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Saturday, September 8th, 2012 AT 2:19 AM

13 Replies

  • Tiny
  • saturntech9
  • Expert
  • 29,868 posts

Have you checked for codes yet?

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Saturday, September 8th, 2012 AT 3:46 AM
  • Tiny
  • tylercovell
  • Member

Well it's not throwing any codes at all.

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Saturday, September 8th, 2012 AT 12:51 PM
  • Tiny
  • saturntech9
  • Expert
  • 29,868 posts

Lets try this remove the negative battery cable for one min then hook it back up. See if that works sometimes all you have to do is give the computer a little reboot like when your cell phone acts up and you turn it off and on again. Let me know what happens.

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Saturday, September 8th, 2012 AT 3:07 PM
  • Tiny
  • tylercovell
  • Member

Ok so I tried that and nothin changed. Now I was thinking, I did clean the throttle body and replaced the gasket, could a vacuum leak from the new gasket not sealing properly possible cause it to act that way?

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Sunday, September 9th, 2012 AT 1:23 AM
  • Tiny
  • saturntech9
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The only reason I wasn't thinking a vacuum leak was because it idles down after a few seconds. It wouldn't hurt to look for a vacuum leak. Also. How is the coolant temp sensor?

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Sunday, September 9th, 2012 AT 2:35 AM
  • Tiny
  • tylercovell
  • Member

I changed that about 6 months ago and alright I'll check and get back with you

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Sunday, September 9th, 2012 AT 4:13 AM
  • Tiny
  • saturntech9
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Alright keep me posted.

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Sunday, September 9th, 2012 AT 5:25 AM
  • Tiny
  • tylercovell
  • Member

So I have been driving the truck and it still does it but I notice it only does it with the ac on.

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Thursday, September 13th, 2012 AT 7:48 PM
  • Tiny
  • saturntech9
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  • 29,868 posts

Does the idle kick up when turning on the ac?

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Thursday, September 13th, 2012 AT 8:43 PM
  • Tiny
  • tylercovell
  • Member

When the truck is sitting still at idle and I turn on the ac it fluctuates every so often like every 45 seconds it's will rev a up from like 600 rpms to about 700 to 750 and drop back to 550-600

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Thursday, September 13th, 2012 AT 9:43 PM

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