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High idle on 1998 chev silverado with 5.7 vortec

The idle is too high in park it is at 1100 rpm, and in gear at about 700rpm. The only way it will drop is by shutting off the truck for a few seconds and then it drops, but as soon as it is driven it will go into high idle again. The fuel consumption has also increased alot.

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Posted on Jan 02, 2017

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SOURCE: idle too high +goes higher when put in gear (manual transmision

IAC valve problem. Nissan has a updated harness (with one way diode inside of the harness) to prevent backfeeding for the IAC valve and a new IAC valve also gets installed. That's where I would look. IAC valve or "idle air control" valve.

Posted on Sep 21, 2008

  • 23 Answers

SOURCE: jeep idles around 500 rpms

check throttle position sensor

Posted on Oct 03, 2008

  • 1450 Answers

SOURCE: Idle on 5.3L Silverado

remove the air intake and clean throttle plate. using a rag and carb cleaner spray it down hold open and wipe down

Posted on Dec 08, 2008

  • 101 Answers

SOURCE: High fuel consumption

Tune up, Change oil, Wires, plugs,PCV, Air filter

Posted on Sep 10, 2009

  • 775 Answers

SOURCE: RPM run high and slow to drop down

a vacuum leak will cause a high idle due to he fact more air is entering the engine which the computer will compensate by adding more fuel. also, a faulty fuel pressure regulator will increase fuel pressure delivering more fuel than required.

look for broken or detatched vacuum hoses. check fuel pressure; 30-50psi

Posted on Apr 09, 2010

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