1991 Camaro 3.1 Service Engine soon.

Tiny
EGILLIAM
  • MEMBER
  • 1991 CHEVROLET CAMARO
1991 Camaro 3.1 289000 miles, NO OTHER PROBLEMS. Just about 2 months ageo I started my car and the service engine soon light came on. Right before that it started idleing rough but not terrible bad (I had to look at my tach to see it bouncing). Also my tach reads way off, I mean when it idles it idles at 2500 rpm and when I am driving it is on the peg (this was happening at leasts 2 years before the service engine soon). Any way the light comes on as soon as I turn the car on. If I unplug the Ingition Control module which I just replaced, the light will not come on till I am about half a mile down the road. I have replaced like I said the ICM as well as the ECM. Any Suggestions or questions?
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Tuesday, March 20th, 2007 AT 7:56 PM

18 Replies

Tiny
SERVICE WRITER
  • EXPERT
I would start by finding what codes are in it, clearing them, and driving until it comes back on, and again recording the codes.
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Tuesday, March 20th, 2007 AT 8:06 PM
Tiny
EGILLIAM
  • MEMBER
I did try that. The code was 42 and it came back within 2 secs. I was thinking it might be the IAC but wanted someone elses opinion before I spent 100$ on a tiny device.
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Tuesday, March 20th, 2007 AT 8:09 PM
Tiny
EGILLIAM
  • MEMBER
I know that my car has lots of miles on the orignal engine but, it does not leak any thing, has no missing, and no knocking. When I start the car up before I pull out it turns the service engine soon light on. Now when it warms up I can mash the throttle and it will run slow until the Tach goes out of the mesurable range then it starts running fine. Just ask I have plenny of info on this stupid thing.
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Tuesday, March 20th, 2007 AT 8:26 PM
Tiny
SERVICE WRITER
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Iac should be a code 35 I think.

42 "may" end up being a computer
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Tuesday, March 20th, 2007 AT 8:31 PM
Tiny
EGILLIAM
  • MEMBER
Thats what I thought to. So I went and replaced it as well. Still did not help. It did fix all the other problems I was having thou.
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Tuesday, March 20th, 2007 AT 8:33 PM
Tiny
SERVICE WRITER
  • EXPERT
Since there are no performance problems, I doubt a wiring short or open. Ignition control module would be the next most probable cause.
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Wednesday, March 21st, 2007 AT 6:13 PM
Tiny
EGILLIAM
  • MEMBER
I tried that to it did not help. Any more possibilities
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Wednesday, March 21st, 2007 AT 6:27 PM
Tiny
SERVICE WRITER
  • EXPERT
Only thing left is wiring, as I understand it. Open or short. Run through the wiring according to the info you have, or I can send what I have.
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Wednesday, March 21st, 2007 AT 6:42 PM
Tiny
EGILLIAM
  • MEMBER
OK that is what I was thinking I have a Chilton s Manuel. It shows the wiring out line I will try that and see what happens thanks aLOT.
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Wednesday, March 21st, 2007 AT 7:04 PM
Tiny
SERVICE WRITER
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I came accross a little more explanatory info if you need it.
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Thursday, March 22nd, 2007 AT 5:50 PM
Tiny
EGILLIAM
  • MEMBER
Yeah if you don't mind I kind of figured mine cannot be the only one in the world that had this probelm
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Thursday, March 22nd, 2007 AT 5:57 PM
Tiny
SERVICE WRITER
  • EXPERT
On its way
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Thursday, March 22nd, 2007 AT 6:13 PM
Tiny
EGILLIAM
  • MEMBER
Sir, Thank you for all your help I have just one more question, The wires that run from the ECU to under the hood do they go under the front right quarter panel?
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Tuesday, March 27th, 2007 AT 9:42 PM
Tiny
SERVICE WRITER
  • EXPERT
Sir?

I really don't know, may have to undo some harnesses to see what colors run through it.
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Tuesday, March 27th, 2007 AT 10:06 PM
Tiny
EGILLIAM
  • MEMBER
Thanks Paul for all your help.
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Wednesday, March 28th, 2007 AT 5:34 PM
Tiny
SERVICE WRITER
  • EXPERT
My pleasure.
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Wednesday, March 28th, 2007 AT 8:34 PM
Tiny
EGILLIAM
  • MEMBER
Here was the problem My car had the check engine soon light and gave the code 42. Well after extensive research I found that Code 42 for a camaro is the ckt between Computer and Distributer, Including the COIL and Wires. Well I replaced everything that was in the path except for the wires from ECM to distributor. That was the next step. So we started testing the cables with the Chiltons Manuel for a camaro. After testing the results stated the Ingition Module was bad so we had it tested at auto zone and it was clear. So we said the only thing left is the wires. Before we replace the wires we notice that the tests were reading very high resistance when the 4 prong connector was connected to the ICM. So we cleaned and made the connectors tighter and it fixed all the problems. Thanks for all your help
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Tuesday, June 12th, 2007 AT 5:11 PM
Tiny
SERVICE WRITER
  • EXPERT
It can be frustrating when test data shows a part that is bad, only to find out otherwise. A shop begins to look "shady" or "is guessing" when this happens.

Glad to hear you got it solved.
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Tuesday, June 12th, 2007 AT 5:43 PM

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