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Old 09-19-2011, 08:27 AM
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New Member with a Problem

Hello all, I have a 2002 Grand Cherokee with the 4.7 HO engine. Bought it as is with 168,000 miles on it. Starting up in the morning it revs up to over 2 grand then down to 100 then jumps all over. After it warms up it settles out around 700 but keeps jumping up once in a while.
Thanks for any suggestions. Dealer charged 300 bucks and change the right manifold o2 sensor but did no good for the repair.
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Old 09-19-2011, 08:50 AM
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Re: New Member with a Problem

I read some of the similar problems and jeepgcoman sent CMSKenny a good reply. This may help me but now I need to know. Where are the O2 sensors and MAP sensor and IAT sensor located or whare can I go to get a diagram?
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Old 09-20-2011, 09:45 PM
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Re: New Member with a Problem

Idle speed is controlled by the PCM via the Idle Air Control stepper motor on the throttle body. This stepper motor plunjer gets quite dirty after some time and the air passage as well, so its a good thing to clean this thoroughly. Here is an other thread with some pictures: Lopey idle on an 02' Overland / 4.7HO
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Old 09-21-2011, 01:58 AM
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Re: New Member with a Problem

The throttle position sensor is a VERY common failure on the 4.7l that causes irratic idle amongst other things...

If you grab the sensor with the car running and give it a jiggle (obviously its not going to move much with the two T20 torx holding it) but just try to move it around a bit. If your idle fluctuates as you do this replace the sensor.
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