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Fast idle concerns...

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Recently, I've had problems with a fast idle problem with my 89 MJ.

Once I start the jeep up to warm up, the RPM's increase as the jeep warms ups. With no tach in the jeep yet, it appears it starts with a respectable 700-900 RPM's. After 10-15 mins of run time, it appears its running 2000+/- RPMs. Once the motor runs this fast, I shut the motor off and go in the house for 10-15+ minutes. When I come out and restart, everything appears to be OK. :doh:

I've replaced the O2 sensor about 4 months ago. I cleaned the throttle body with TB cleaner the other day- a little oily. Maybe the idle air control valve is bad? Maybe a vacuum leak?

Any thoughts?

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  • 5 months later...

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