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High idle?

Tiny
DANNY SPIKES
  • MEMBER
  • 1995 BUICK LESABRE LIMITED
  • 3.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 140,000 MILES
The car idles from 1,500 to 3,000 RPMs. I have replaced the idle air control valve, the throttle position sensor, the MAP sensor, the temperature sensor and the oxygen sensor. My code reader only goes back to a 1996, but I borrowed a Snap-On high dollar reader it hooks up but will not read codes from the computer. Thanks
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Saturday, December 9th, 2023 AT 9:54 AM

14 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
I have seen the EGR valve stick open and cause this problem. Also, here is how to run the codes for this car to see if any are stored:

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

This guide can help as well:

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

Here is the location of the EGR so you can remove it to see if it is leaking. These valves go bad btw. Check out the images (below). Please upload pictures or videos of the problem so we can see what's going on.
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Saturday, December 9th, 2023 AT 10:20 AM
Tiny
DANNY SPIKES
  • MEMBER
  • 8 POSTS
There is one more thing I did on this car, but it was idling high before I did it. The key was loose in the ignition so I read the key to find out what the ohm's were and found it to be 4.5 so I got a 4.5 ohm resister and cut the wires to the switch and soldered the resister in.
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Monday, December 11th, 2023 AT 3:38 PM
Tiny
KEN L
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Can you please follow the code guide I linked to above? It takes a small piece of wire to do so. Also, is the check engine light on?
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Tuesday, December 12th, 2023 AT 11:50 AM
Tiny
DANNY SPIKES
  • MEMBER
  • 8 POSTS
Thanks Ken, I will do that when I get back to my shop. I think this car has an 0bd2 set up " I will double check that" I do know my 0bd2 scanner will plug right into it but will not read the codes. I have replaced all the sensors I ordered all of them for a 1995 Buick Lesabre. Could I have sensors for a 0bd1 system and actually have the 0bd2 system? And will the 0bd2 system work with the jumper? I am old school mechanic started in 1970 with a ford dealership but have not done much on electronic controlled auto's. I thank you for all your advice, Lord knows I need all I can get. Thanks again.
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Tuesday, December 12th, 2023 AT 1:45 PM
Tiny
DANNY SPIKES
  • MEMBER
  • 8 POSTS
Ken, I tried the jumper wire test you were talking about but got no response from it when I switched the car on. The check engine came on but never flashed. I am going to try to send a video of the car running. You will see it idling at about 2,000 RPMs and go to 3,000 RPMs and I never touched the accelerator. I am also sending a photo of the 0bdi port. Any other info I can get for you please let me know.
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Wednesday, December 13th, 2023 AT 1:05 PM
Tiny
KEN L
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Thanks for the image and video they help, The PCM should have responded to one of the scan methods. Let's check fuse # 9C in the fuse panel on the left side of the dash and if the fuse is okay, it sounds like the PCM is bad so I would remove it to have it tested or replaced with a rebuilt unit. You can get a preprogrammed unit by searching Google or Ebay. Here is how to change the PCM out.

REMOVE OR DISCONNECT

Disable Supplemental Inflatable Restraint (SIR) system.

1. Powertrain Control Module (PCM) connectors.
2. PCM.

Pull bottom of PCM rearward over locking tabs and downward to remove.

INSTALL OR CONNECT
1. PCM into bracket, making sure PCM is up over locking tabs and locks into place.

2. PCM connectors.

Enable SIR system.

Check out the images (below). Please let us know what happens.
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Thursday, December 14th, 2023 AT 11:06 AM
Tiny
DANNY SPIKES
  • MEMBER
  • 8 POSTS
Thanks, I have checked the fuse it is good. I sure do thank you for your help, when I get a chance to change the PCM I will let you know if that fixed it. Thank you, Dannd D.
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Thursday, December 14th, 2023 AT 12:15 PM
Tiny
KEN L
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You are welcome, the PCM should fix the problem but also please make sure there is nothing holding the throttle open such as a floor mat etc.
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Saturday, December 16th, 2023 AT 10:00 AM
Tiny
DANNY SPIKES
  • MEMBER
  • 8 POSTS
I have checked all that. Also, what I have found in my research is that I have what is called an obd1.5. The computer is obd1 and the port is obd2, it is very hard to find something that will read the codes. The jumper will not work on this system. But that is my luck to have an oddball. Thanks
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Sunday, December 17th, 2023 AT 11:35 AM
Tiny
KEN L
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The fact that you can't get any codes from the PCM is telling us it could be bad.
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Monday, December 18th, 2023 AT 9:41 AM
Tiny
DANNY SPIKES
  • MEMBER
  • 8 POSTS
I have one ordered, That's my next step. Thanks
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Monday, December 18th, 2023 AT 12:08 PM
Tiny
KEN L
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Sounds good, please let us know what happens.
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Tuesday, December 19th, 2023 AT 12:14 PM
Tiny
DANNY SPIKES
  • MEMBER
  • 8 POSTS
Well, to let you know I got the PCM this morning and installed it in the car. The car cranked and ran fine no more high idle. Thanks
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Tuesday, December 19th, 2023 AT 12:38 PM
Tiny
KEN L
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Thanks for letting us know, we are here to help, please use 2CarPros anytime.
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Thursday, December 21st, 2023 AT 9:41 AM

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