Shuts off when in gear at no throttle?

Tiny
TRAV1173
  • MEMBER
  • 1999 GMC S15
  • 4.3L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 130,000 MILES
Does not idle.
Monday, March 6th, 2023 AT 3:11 PM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

This type of issue can be the result of a few things. Most commonly, it is an engine vacuum leak. Also, the vehicle has an idle air control valve (IAC) that is responsible for maintaining engine idle speed.

Here is what I suggest: First, check for engine vacuum leaks.

Here is a link that explains how it's done:

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

If you are unable to find a leak, the next thing to do is check the IAC. The IAC is located on the throttle body. Pic 1 is very vague but that is what the manual provides.

Remove the IAC and check for carbon or corrosion restricting air where the IAC's pintel enters the throttle body. If there is excessive build-up, use carb cleaner, and clean it as best as possible along with the pintel valve.

Here is a link that explains how (in general) to service an IAC:

https://www.2carpros.com/articles/idle-air-control-valve-service

Let me know what you find. Also, if the check engine light is on, let me know if you had the computer scanned for codes and what they are.

Take care,

Joe

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Monday, March 6th, 2023 AT 8:54 PM

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