Engine idling high

Tiny
MICHELLERAKESTRAW
  • MEMBER
  • 1998 ISUZU RODEO
  • 264,000 MILES
Going about 25 miles per hour without me putting my foot on the gas. Please help.
Saturday, May 28th, 2022 AT 3:05 PM

5 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

Did this happen all at once? Does the check engine light stay on when the engine is running?

This vehicle has a throttle cable that may need to be adjusted or is damaged from age and not allowing the throttle to fully close.

I attached the directions below for adjustment. Try this. Also, inspect the cable both at the throttle body under the hood and in the vehicle at the throttle pedal for indications of fraying or anything that may cause it to stick.

If you question anything, disconnect the cable at the throttle body to make sure it is fully returning to the closed position. I attached a few additional pics so you can see the cable, where it is routed, and how it is connected at the TB.

Let me know.

Take care,

Joe

See pic below.
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Saturday, May 28th, 2022 AT 11:28 PM
Tiny
MICHELLERAKESTRAW
  • MEMBER
  • 1 POST
Hi Joe, thank you so much for your time. I am so depressed about my new ride. Anyway, I have someone that says they will come over tomorrow and look at your instructions. I so appreciate your time. I will let you know what happened soon as I know something. Good night and God bless, Michelle, forever grateful.
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Sunday, May 29th, 2022 AT 9:43 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,690 POSTS
Joe F is one of our best! Use 2CarPros anytime, we are here to help. Please tell a friend.
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Sunday, May 29th, 2022 AT 9:43 AM
Tiny
MICHELLERAKESTRAW
  • MEMBER
  • 1 POST
Hi, can transmission fluid being low effect the idle running so high? Thank you, my friend checked what you advised, and it wasn't. Thank you so much, Michelle
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Monday, May 30th, 2022 AT 1:25 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Michelle,

The transmission fluid wouldn't cause this. If the throttle cable is in good condition and the throttle body is fully returning to the idle position, the next thing we need to check is for an engine vacuum leak.

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 locate any leaks, then we need to focus on what is called the idle air control valve (IAC). The IAC is responsible for maintaining idle speed. If you look below, I provided the directions for cleaning, inspecting, and measuring the pintle valve. (See pic 1)

Pics 2 and 3 are the directions for removal and installation. Also, here are two links you may find helpful:

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

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

If you follow the air intake tube from the air filter box, it will lead you to the throttle body.

Let me know what you find or if you have other questions.

Take care,

Joe

See pics below.

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Monday, May 30th, 2022 AT 7:29 PM

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