My Car Idles too high at start.

Tiny
AO7777
  • MEMBER
  • 1995 BUICK CENTURY
  • 165,440 MILES
My 1995 Buick Century idles too high after I start the car. I find no vacuum leak However I do have a check engine soon light on and I don't know if the Idle position sensor is doing it. I have a the newer 3.1 V6 SFI Engine not the V6 3.1 MFI. Before all this, My Car was given to a friend of my wife's and we told her now to let no body, and I mean no body to touch the car for any reason. Well, she didn't obey, and her children tried to steal it and they tried to jump another car and the positive + jumper connector touched the air cleaner cover, (metal) and cause a engine fire and instead of diconnecting the negative wire connector - they looked on and let the wire burn until they got some dirt and stopped the fire, in 2 different places. My wife and I had the car towed to our house and there I bought a whole complete engine wiring harness and replaced the burnt one. Does that make you mad! Help me with this problem and get this car up and running again like it once did. Also can it be the ECM? How can I check if its bad? Thx u.
Sunday, July 22nd, 2012 AT 2:43 AM

13 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
With what you describer, yes, I believe the ecm is fried. I would replace it as if it is not bad now, it will be.

The idle air control may be your issue with the cold high idle.

Roy
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Sunday, July 22nd, 2012 AT 2:48 AM
Tiny
AO7777
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Thx u ASEMaster6371. You still didn't answer the question about how to check if the ECM is good or bad? I may have to borrow a ECM with serv number that matchs mine to see there any difference. Thx u.
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Sunday, July 22nd, 2012 AT 3:00 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
You cannot unless you have the equipment. A real scan tool that can monitor sensors. Looking at the inputs and outputs and there needed and real values.

Roy
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Sunday, July 22nd, 2012 AT 11:54 AM
Tiny
AO7777
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  • 17 POSTS
Is the Idle air control is the Throttle position Sensor? If not, tell me were it is located. Also, what should I start 1st? Get an ecm or get a new TPS? I believe the TPS is working, need to know how to test the TPS.
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Sunday, July 22nd, 2012 AT 10:40 PM
Tiny
DJCL
  • MECHANIC
  • 767 POSTS
To test the tps get a dvom. There are 3 wires one is a ground one is a 5 volt ref voltage. And one will be the signal wire. There is no adjustment for it on this car. The koeo voltage will range from about.2 volts to about 4.9 volts at wot. The best way to test it is with a grafing meater.
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Monday, July 23rd, 2012 AT 12:12 AM
Tiny
AO7777
  • MEMBER
  • 17 POSTS
So far, I found the fuel leak, from the fuel intake hose, so I replace both the intake and relief lines. As soon after I started the car, I did smell some fuel yet no leaks from the hoses until after I discovered a fuel leak from under the plenum intake manifold but not from the hose were is screwed on at. Can a injector be leaking and cause the idle to idle high (vacuum leak)? I had some small trouble putting the plenum intake manifold on lining up the holes before screwing down the screws. Yet nothing seemed to binding before installation of the plenum.
What did I do to cause the fuel leak?
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Sunday, August 5th, 2012 AT 11:28 PM
Tiny
AO7777
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  • 17 POSTS
I forgot, when I started the engine, I had the TPS disconnected and yet no change in idle. However, I shut off the car and reconnected the TPS and disconnected the IAC valve and again started up the car and the idle seemed much lower but when I reconnected the IAC valve, the idle shot up again like it was doing before. Can the IAC valve be the problem or that fuel injector leak?
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Sunday, August 5th, 2012 AT 11:34 PM
Tiny
AO7777
  • MEMBER
  • 17 POSTS
Hello, I am back. I changed the ecm and still the problem exists. I have a friend who is a mech and he told me that the TPS is the problem. I bought a obd1-obd2 scanner and its on the way. I will find out what is the problem is.
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Saturday, August 18th, 2012 AT 2:19 AM
Tiny
AO7777
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I recieved the Scanner and get to find out, through tech support, that the scanner I bought cannot read the ecm for this car. I need to know what scanner or code reader do I need to read the codes.
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Thursday, August 23rd, 2012 AT 12:08 AM
Tiny
AO7777
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I had a lot of dought about their answers about my new scanner. However, I found out that my obd1 scanner does not work and has now power. It also has a factory Security Alarm but I removed it. But my 12 pin connector has no power and only has 3 wires coming out from the back of the obd1 connector. No "B" terminal, I have a obd1 scanner and does not read it.
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Saturday, August 25th, 2012 AT 2:27 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Ok, the no power could be a blown fuse as the fuse for the cigar lighter may be that issue.

The idle air control may definitely may be bad from the voltage surge from the wrong jumping.

Was this harness from an exact car? Did you replace the ecm with a new one? Did you jump the connector to flash out any codes?

Roy
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Sunday, August 26th, 2012 AT 1:08 AM
Tiny
AO7777
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  • 17 POSTS
Msg to Roy. Thx u roy, so far, there is no blown fuse, cigar lighter has power, question, does this paticular vehicle 12 pin DLC have to have a power wire in order to use a scanner to read the codes? Terminals A and B, there is no wires, just on the left side, 1st 2 on the top and 1 on the bottom left? I cannot jump the A and B Terminal because there isn't a A and B Terminal. How do you jump them? I did get the right harness from the exact car, the exact 1995 car, I have to go to the part dept at a gmc dealership. I did not replace the ecm. That why I wanted to check the ecm with a scanner to see if any problems, yet I cannot. It cannot communicate with the ecm. Let me know what else. Thx u.
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Sunday, August 26th, 2012 AT 1:34 AM
Tiny
AO7777
  • MEMBER
  • 17 POSTS
Msg to roy, I replaced the IAC and still its idling very high. I do not see or hear any vacuum leaks at all. All I know that when I start the car, there is no SERVICE ENGINE SOON that comes on until the IDLE start going up and then the SERVICE ENGINE SOON light comes on. I did changed the ecm also before I got the IAC and still the idle comes on. This is something that I am coming to the end and don't know what to do. I need help really bad. Thx u.
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Saturday, September 15th, 2012 AT 11:06 PM

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