High idle after car has been driven for a while

1997 MITSUBISHI GALANT
95,000 MILES • 2.4L • 4 CYL • FWD • AUTOMATIC
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TEDWILLIAMS2260
  • MEMBER
  • 6 POSTS
Engine idles high when coming to a stop, around 1200rpm, also happens when I stop and shift to reverse from drive. Seems to happen when the car has been driven for about 15 minutes and longer.

Has a steady smooth idle, can't hear any vacuum leaks, just idles high intermittently.
Nov 13, 2015 at 4:05 AM
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WRENCHTECH
  • ✓Experienced Mechanic
  • 20,760 POSTS
You won't necessarily hear a vacuum leak

You may have a bad IAC ( idle air control) but try eliminating any vacuum leaks and cleaning the throttle body first. Remove the intake snorkel, have someone hold the throttle wide open for you and scrub the back side of the throttle plate and surrounding bore with an old tooth brush and some carb cleaner. Be sure to spray some into the small holes next to the throttle plate. That should help stabilize the idle. If it still has a problem, replace the IAC.
Nov 13, 2015 at 4:36 AM
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TEDWILLIAMS2260
  • MEMBER
  • 6 POSTS
I'll try what you recommend.


Thanks
Nov 13, 2015 at 9:08 PM
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