Stops running when you let off gas

Tiny
THOMASERD
  • MEMBER
  • 1994 CHEVROLET LUMINA
  • 3.4L
  • V6
  • 2WD
  • AUTOMATIC
  • 107,000 MILES
It is a 1994 Chevrolet Alero APV Auto. When I stop or just sit in the yard now let off the gas I will shut off but It will be right back up. What could be the issue with that? Could have been idler physician air flow thing.
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Sunday, November 4th, 2018 AT 6:14 PM

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Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi and thanks for using 2CarPros.com.

This could be a couple things. Most commonly, the idle air control valve (IAC) is carboned or bad. The IAC is responsible for maintaining the engine idle speed. If it fails, the engine will stall when you take your foot off the gas.

Also, an engine vacuum leak can cause this type of problem. Here is a quick link that shows how to locate a leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

What I suggest is to first remove the IAC and inspect it for dirt or debris. Also, where the pintle enters the throttle body, make sure there is no carbon or debris there as well.

Here is a link that shows an IAC being replaced. It may help you with locations and procedures. Basically, it should help give you a good understanding of what will be done.

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

Here are directions for replacement specific to your vehicle. The two attached pictures correlate with these directions.

__________________

IDLE AIR CONTROL (IAC) VALVE REPLACEMENT
Intake Air Control Housing

REMOVAL:

1. Disconnect the idle air control (IAC) valve electrical connector.
2. Remove the IAC valve attaching screws.
3. Remove the IAC valve assembly.

CAUTION: On IAC valves that have been in service, DO NOT push or pull on the old IAC valve pintle. The force required to move the pintle may damage the threads on the worm drive.

4. Clean the IAC valve O-ring sealing surface, pintle valve, seat and air passage.
Use carburetor cleaner and a parts cleaning brush to remove carbon deposits. DO NOT use a cleaner that contains Methyl Ethyl Ketone. It is an extremely strong solvent, and not necessary for this type of deposit.
Shiny spots on the pintle or seat are normal, and do not indicate misalignment or a bent pintle shaft.
If the air passage has heavy deposits, remove the throttle body for complete cleaning.
Inspect the IAC valve O-ring for cuts, cracks or distortion. Replace if damaged.

NOTE: If installing a new IAC valve, be sure to replace with an identical part. IAC valve pintle shape and diameter are designed for specific application.

Idle Air Control Valve

INSTALLATION:

1. If installing a new IAC valve, measure the distance between the tip of the pintle and the mounting flange.
If greater than 28 mm, use finger pressure to slowly retract the pintle. The force required to retract the pintle of a new valve will not cause damage to the valve.
2. Lubricate the IAC valve O-ring with clean engine oil.
3. Install the IAC valve assembly.
4. Install the IAC valve attaching screws, and tighten to 3.0 Nm (27 in lb).
5. Connect the IAC valve electrical connector.
6. START the engine and allow it to reach operating temperature.

NOTE: No physical adjustment of the IAC valve assembly is required after installation. The IAC valve is reset by the PCM when the ignition is turned ON, and then OFF.

__________________________________-

Let me know if this helps or if you have other questions.

Take care,
Joe
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Monday, November 5th, 2018 AT 8:05 PM

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