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Will crank and run but does not idle, there are no codes?

Tiny
DSTHOE
  • MEMBER
  • 1989 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 270,000 MILES
Will crank and run but won't idle, there are no codes?
Saturday, December 10th, 2022 AT 4:52 AM

3 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,665 POSTS
This can happen when the engine has a vacuum leak or the idle air control motor stops working, here is a vacuum leak detection guide that should be used when the engine is cold only and the location of the IAC valve which you should replace if there are no vacuum leaks.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

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Saturday, December 10th, 2022 AT 12:25 PM
Tiny
DSTHOE
  • MEMBER
  • 1 POST
Replaced IAC still want idle, is there a way to check to see if IAC is communicating with computer? No vacuum leak.
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Monday, December 12th, 2022 AT 12:41 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,665 POSTS
Yes, remove the IAC and then plug it in and turn the ignition on, the IAC should move outward or inward. Let me know.
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Monday, December 12th, 2022 AT 12:42 PM

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