When at idle the RPMs increase and decrease dramatically

Tiny
NOTTUH
  • MEMBER
  • 1986 HONDA PRELUDE
Hello, it is fuel injected. My question is a diagnosis problem. When at idle the rpms increase and decrease dramatically and at a fast rate.I checked for a vacuum leak any thoughts?/
Tuesday, May 13th, 2008 AT 2:45 PM

1 Reply

Tiny
SQM
  • MECHANIC
  • 6,383 POSTS
Hello,

This issue is likely a faulty idle air control valve. Honda calls it the fast idle valve.
It is located on the intake manifold (see diagram).
Over time the valve can accumulate dirt and debris and create idle issue like you are experiencing.
Sometimes cleaning out the valve can improve the idle.

https://www.2carpros.com/articles/idle-air-control-valve-service

I have attached diagrams and the test procedure for the valve.

Please let me know if you have any questions.
Thank you.
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Wednesday, October 27th, 2021 AT 9:53 AM

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