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RPM's fluctuate

Tiny
MNT8092
  • MEMBER
  • 2001 FORD MUSTANG
  • 117,000 MILES
My car runs perfect except for at a red light after forty five minutes of driving the rpm's fluctuates 500 to 900 rpm's. Almost everything has been replaced. It drives me crazy. I get thirty two miles on the highway. I have another car same model/year and same engine and it does not do that. Thanks if you can help.
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Monday, March 5th, 2018 AT 2:50 PM

3 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning.

There is an Idle air control valve that keeps the idle steady. Have you looked at this yet?

Roy
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Tuesday, March 6th, 2018 AT 5:11 AM
Tiny
MNT8092
  • MEMBER
  • 2 POSTS
Yes, I have replaced everything. I am wondering if it could be my brake booster. Nothing leaking.
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Tuesday, March 6th, 2018 AT 12:33 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
It sounds more like you have a dirty throttle bore and IAC motor. Here is a guide to help you see how to fix it:

https://www.2carpros.com/articles/throttle-actuator-service

Please let us know what happens.

Cheers, Ken
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Thursday, March 8th, 2018 AT 12:37 PM

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