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davealberta 02-17-2012 12:00 PM

Engine RPM flucuating at Idle
I have just purchased a 1999 WJ with a 4.7L engine.
When I start the engine from cold the rpm flucuates back and fourth between 2000 rpm and 1000 rpm. When I put in drive and drive the vehicle everything is fine.

It idles about 750 rpm when warm, but occasionally flucuates in idling for awhile.

Any suggestions on the possible cause would be appreciated.

I am uncertain as to whether sparks plugs or other items had been serviced prior to my buying the vehicle.

Frango100 02-17-2012 12:41 PM

Re: Engine RPM flucuating at Idle
Fluctuating rpm at idle is often caused by a dirty idle air passage and Idle Air Control motor plunjer in the throttle body. Clean this very well and try again.
Is it still fluctuating, then it is probably the TPS sensor.
Also when you donīt know the history of the jeep, its good to change all oils/fluids/filters etc.

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