High idle issue

Tiny
SNEDWARDS39
  • MEMBER
  • 1991 BUICK SKYLARK
  • 2.5L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 100,000 MILES
My vehicle has a very high idle, so I replaced the IAC and the TPS and also the EGR valve. Still nothing changed, it still idles high and when driving it the car will actually push you to the point that it's difficult to stop sometimes. I need help!
Sunday, May 8th, 2022 AT 11:07 PM

9 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,071 POSTS
Hi,

This vehicle has a throttle cable that runs from inside the vehicle to the throttle body. Often times they fray and can prevent the throttle from releasing. Have you inspected the cable from end to end? Also, it is adjustable. Have you tried adjusting it?

I attached the directions for adjustment below. The easiest thing to try is this: Disconnect the cable at the throttle body and see if the idle lowers.

Let me know what you find.

Joe

See pics below.
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Monday, May 9th, 2022 AT 7:11 PM
Tiny
SNEDWARDS39
  • MEMBER
  • 7 POSTS
It doesn't idle high all the time the idle does lower at times. But I will look at the cable and let you know.
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Monday, May 9th, 2022 AT 7:52 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,071 POSTS
Hi,

Sounds like a plan. They do wear and this can happen. The easiest way to test if it is the cable is to simply disconnect it at the throttle body to see if that eliminates the high idle.

It is very possible this is the issue.

Let me know what you find. Also, let me know if you checked to see if there are any engine vacuum leaks. That can cause idle issues as well. If you haven't checked, here is a link that explains how to check:

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

Take care and I'll watch for your reply.

Joe
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Monday, May 9th, 2022 AT 8:02 PM
Tiny
SNEDWARDS39
  • MEMBER
  • 7 POSTS
There are no leaks have already checked. Funny thing is we unplugged the IAC and the car ran better than ever with no idle issues.
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Monday, May 9th, 2022 AT 10:50 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,071 POSTS
When you had it removed, did you inspect where it mounts inside the throttle body for excessive corrosion or carbon?

Joe
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Tuesday, May 10th, 2022 AT 6:50 PM
Tiny
SNEDWARDS39
  • MEMBER
  • 7 POSTS
Yes, we didn't see any but did notice the cable does have some slack in it. Also, now would a bad computer make it run the way it is?
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Friday, May 13th, 2022 AT 7:51 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,071 POSTS
Hi,

It is possible that the PCM could cause the issue. However, it usually isn't the cause. Were you able to disconnect the cable to see if it made any difference?

Let me know.

Joe
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Friday, May 13th, 2022 AT 8:16 PM
Tiny
SNEDWARDS39
  • MEMBER
  • 7 POSTS
Have not disconnected that yet going to try that another thing the speedometer chooses to work when it wants.
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Friday, May 13th, 2022 AT 8:19 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,071 POSTS
Hi,

The speedometer is likely a different issue. Pay attention to how the vehicle shifts when it doesn't work.

If you want, see if you can retrieve diagnostic trouble codes. This vehicle has an OBD1 system and doesn't require a scan tool. All you need is a short jumper wire or even a paper clip. Here is the link that explains how it's done. This may also help with the idle issue.

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

Let me know what you find out with the cable. Also, if you do find codes, let me know what they are.

Take care,

Joe
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Friday, May 13th, 2022 AT 8:26 PM

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