Edmunds Answers

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  • avatar karjunkie 01/29/10 8:50 am PST

    An engine running at very high, low or erratic RPM is usually, 99 times out of a hundred, caused by a dirty IAC (idle air control) valve which is attached to the throttle body. The IAC is what provides the enriched fuel/air ratio to the engine at idle when cold so if it’s too dirty from the black gunk that forms inside the throttle body to function properly, a bad or high idle or an engine that dies at idle when cold is the usual result. Cleaning the IAC is easily done with a toothbrush and spray throttle body cleaner after removing it from the throttle body which is easily done by just removing the one or two torx-head screws that hold it in place. Once it is clean, together with the hole the IAC’s plunger fits into, use the remainder of the TB cleaner to clean out the inside of the throttle body per the instructions on the can. While you're at it, I would also check the EGR valve and clean it as well with the throttle body spray as a gunked up IAC usually means a gunked up EGR. Good luck and let us know if you have any follow up questions.

Answers

  • karjunkie 01/29/10 8:50 am PST

    An engine running at very high, low or erratic RPM is usually, 99 times out of a hundred, caused by a dirty IAC (idle air control) valve which is attached to the throttle body. The IAC is what provides the enriched fuel/air ratio to the engine at idle when cold so if it’s too dirty from the black gunk that forms inside the throttle body to function properly, a bad or high idle or an engine that dies at idle when cold is the usual result. Cleaning the IAC is easily done with a toothbrush and spray throttle body cleaner after removing it from the throttle body which is easily done by just removing the one or two torx-head screws that hold it in place. Once it is clean, together with the hole the IAC’s plunger fits into, use the remainder of the TB cleaner to clean out the inside of the throttle body per the instructions on the can. While you're at it, I would also check the EGR valve and clean it as well with the throttle body spray as a gunked up IAC usually means a gunked up EGR. Good luck and let us know if you have any follow up questions.

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