RPMs at Idle

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10-03-2018, 02:47 PM

X1997J

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Location: Pleasanton, CA

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Year: 1997

Model: Cherokee (XJ)

Engine: 4.0

RPMs at Idle

After coming to a stop like at a red light my rpm at idle is around 600 after sitting there for about a minute the rpm drops to 400. Is this normal?

2003 WJ Limited 4.7 v8

Thanks.

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10-04-2018, 11:41 AM

Rooch1008

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Location: Dutchess county NY

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Year: 2004

Model: Grand Cherokee

Engine: 4.7

Its not normal...my 2004 4.7 does the same thing intermittently...and then it sets off a P302 code...it hasn’t done this for the last 3 or 4 months but it just happened again last week!!!! I’m wondering if it has something to do with the cooler weather...all summer it was fine...no problems or codes...it seems like the 1st morning it was below 60 degrees , the idle and code happened..

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10-04-2018, 12:28 PM

X1997J

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Join Date: Jul 2014

Location: Pleasanton, CA

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Year: 1997

Model: Cherokee (XJ)

Engine: 4.0

Mine does this everyday. Wonder if its the TPS or IAC. Maybe both?

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10-04-2018, 03:57 PM

dave1123

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Location: Manlius, east of Syracuse, NY

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Year: 2000 XJ Sport & WJ Laredo

Model: Grand Cherokee (WJ)

Engine: 4.0L

Try cleaning the IAC. It tends to get sticky when it's damp out if it's dirty. A new Mopar IAC costs about $175, so clean it, don't just replace it. Be sure the port is clean as well. Throttle Body Cleaner and a toothbrush. Be very gentle with the piston on the end of the motor.

Last edited by dave1123; 10-06-2018 at 03:25 AM.