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Low RPMs

Tiny
SAWMAN2424
  • MEMBER
  • 2002 JEEP GRAND CHEROKEE LAREDO
  • 4.0L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 200,000 MILES
Idle speed is down to 550 RPMs. Changed throttle position sensor. Scanner reads 0 codes. At 200,000 miles going down the highway, it runs perfect. Stop at a light rpm drops and has stalled a couple times. Starts back no problem.
Monday, March 22nd, 2021 AT 6:44 PM

1 Reply

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
More then likely this is an issue with idle air control valve. This controls the amount of air that comes in to set the idle speed during deceleration and at idle.

You have what is called a stepper motor so basically the PCM remembers how many "steps" it took to achieve a specific engine speed and it continues to set it at this point but when the valve wears out it may be in that position but the air is restricted or wide open allowing in the wrong amount of air.

If it were me, I would replace this and go from there. Some can be cleaned but it is best to replace yours due to it being a stepper motor.

https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

Below is the process from the manual to replace this. Let me know what happens. Thanks
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Wednesday, March 24th, 2021 AT 4:15 PM

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