Very high idle

Tiny
BENNIE FORD
  • MEMBER
  • 1996 CADILLAC ELDORADO
  • 4.8L
  • V8
  • AUTOMATIC
  • 160,000 MILES
High idle when driving it will slowly pick up speed. I have replaced TPS and sensors on throttle body.
Tuesday, September 11th, 2018 AT 8:36 AM

2 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi and thanks for using 2CarPros.com.

Have you already replaced the idle air control valve (IAC)? The IAC is what maintains engine idle speed. Here are the directions for replacement and the first picture below is the component itself and where it is located:

Removal Procedure

Notice: Numbers in text correspond to numbered components in image.

1. Remove the Idle Air Control (IAC) valve electrical connector.

2. Remove the two IAC valve attaching screws (4).

3. Remove the IAC valve (1).

Installation Procedure
1. Install the new IAC O-ring.

2. Install the IAC valve and tighten the screws. Tighten screws to 3 Nm (27 lb in).

3. Connect the IAC valve electrical connection
__________________________________________________________

If this component has already been replaced and is working, the next thing I would recommend checking is for engine vacuum leaks. Unmetered air into the combustion chamber can increase the idle speed. Here is a link that shows how it is done:

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

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

Take care,
Joe
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Tuesday, September 11th, 2018 AT 6:33 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi again. I wanted to add another link that you may find helpful. It discusses causes of a high idle and ways to repair them.

https://www.2carpros.com/articles/engine-idles-too-high

Let me know if this helps.

Joe
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Wednesday, September 12th, 2018 AT 7:42 PM

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