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Old 02-05-2015, 02:05 PM
stu454's Avatar
stu454 stu454 is offline
Join Date: Dec 2004
Location: Atlanta, GA
Posts: 5,305
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I've brought this one over from the old "tech" tab. No author was listed.

Stepper Motor / Idle Air Control Valve (IACV)

Also called the "Idle bypass valve" and "Idle air control motor". This motor is located on the upper plenum of your rover and allows idle air to flow around the throttle plate when its closed.
Its needed because when your foot is not on the gas the throttle plate is completely closed and shuts off air to the engine. If the engine has no air it obviously cannot idle. The "Stepper motor" controls a small pintle that fits into a passage, this passage channels air around the throttle plate. When the motor is retracted the engine idles up, when it extends it idles down. The motor also compensates for engine loads at idle speeds. You turn the A/C on and it drags the motor down, the "Stepper motor" brings the RPM back in range. The same happens when any load hits the engine at idle.

With that said, it should be pretty obvious what the symptoms of a bad or dirty motor are. Your engine will not want to idle. Or it will idle low and stall when a load such as A/C or Power steering.

To service you will have to remove the motor from the plenum and clean the end of the valve. You should also clean the passage that it fits into with carb cleaner. If the symptoms remain after cleaning the motor more then likely needs to be replaced.
Attached Images
File Type: jpg iac.jpg (33.4 KB, 86 views)
File Type: jpg iac2.jpg (30.7 KB, 79 views)

'07 LR3
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Old 02-06-2015, 02:43 PM
Levi's Avatar
Levi Levi is offline
Join Date: Jul 2004
Location: Cheyenne, WY
Posts: 500
Thought I would add parts cross-references and numbers since you posted this.

94-95 3.9L Cross Reference w/95 Chevy 1500 with 5.0L.
PN: Napa MPF217388, AC 25527027

96-99 4.0L Cross Reference w/96 Jeep Grand Cherokee 4.0L.
PN: AC 151

The cross references came from old posts I remembered and the parts numbers came from the old tech section.

Last edited by Levi; 02-06-2015 at 05:58 PM.
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