Question about GMC Yukon

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Surging idle 1999 yukon slt 5.7 having idle surges, high and low. i've relaced the IAC, cleaned the throttle body, replaced plugs and wires, the main engine computer was replaced 7 months ago but at crank idle drops then surges over 1000rpm then drops to normal. Is also surging up at times while driving. Help

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  • GMC Master
  • 14,398 Answers

Bad throttle position sensor.

Posted on Nov 24, 2013

  • CiCiYuk
    CiCiYuk Nov 24, 2013

    Thank you, I'll look into that. I originally had the IAC changed a year ago due to idle rpm increasing. After awhile it started doing the opposite and dropping and in the last few months started stalling when putting into park. Is there a way to check the throttle sensor or just a replacement and where is it located please?

  • CiCiYuk
    CiCiYuk Nov 28, 2013

    Update 11/26/13: Changed air filter on Sunday and so far no idle surges

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Posted on Jan 02, 2017

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csmock132
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SOURCE: 1989 GMC 2500 5.7L - engine surges and stalls at idle. Loses power at cruising speed.

Wow you have replaced a lot of stuff. Lets go back to the Fuel pump. When you replaced it did you replace the hose between the pump and the sending unit. These are common for splitting. Have you hooked up a fuel pressure gauge to check what pressure you have? It should be real close to 13 psi and should raise to at least 18 or 19 when you pinch off the return line.

Posted on Jun 02, 2009

csmock132
  • 4669 Answers

SOURCE: 2001 taurus dohc codes 171

There is a large vac line coming straight down from the throttle body that goes to the PCV system. See if it has a hole in it. It is likely sucking air.

Posted on Jul 17, 2010

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