Rpm's fluctuate

2001 FORD MUSTANG
117,000 MILES
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MNT8092
  • MEMBER
  • 2 POSTS
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.
Mar 5, 2018 at 6:50 AM
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ASEMASTER6371
  • ✓Experienced Mechanic
  • 52,796 POSTS
Good morning.

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

Roy
Mar 5, 2018 at 9:11 PM
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MNT8092
  • MEMBER
  • 2 POSTS
Yes, I have replaced everything. I am wondering if it could be my brake booster. Nothing leaking.
Mar 6, 2018 at 4:33 AM
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STRAILER
  • ✓Experienced Mechanic
  • 55,554 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
Mar 8, 2018 at 4:37 AM
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