99 Grand Am hard start / no start

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4 years 11 months ago #33854 by JimO
JimO created the topic: 99 Grand Am hard start / no start
A friend bought this car after it had sat for over 1 1/2 years with out me looking at it first. As you can imagine alot was bad from sitting so long. Brakes being the biggie. The engine is the 3.4 with over 159K. After a week the main head ache turned out to be that the car would stall out and not restart. Cold it would start fine. As it warmed up it became progressivly hard to start. It would start and stall in the run possition. You had to feather the throttle to keep it going. Eventually it would not start at all. Other friends and the owner insisted I change the fuel pump believing the tank was full of rust even though I had 40 psi. The tank was clean inside. I told the owner the old put was still good but he wanted the new one. So I did and the problem continued. No engine codes. When it would not restart I used my clipon stark plug and found no spark. Took off the ICM and had it tested at Auto Zone. It passed all 15 times. Problem continued. Used my Snapon MT2500 still no codes and reading looked good. Long story short I replaced the ICM anyway and the problem was corrected. I beleive that as the old ICM warmed up with the car it began to fail. It had cooled by the time I took it off to test it and did not get as hot during the test. My 96 Old 88 with the 3.8 had the same problem 4 years ago except the Olds just stopped running. Hope this helps someone.

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4 years 11 months ago #33866 by W00DBar0n
W00DBar0n replied the topic: Re: 99 Grand Am hard start / no start
I've heard about that happening a lot with "older" GM cars before, but i didn't think a 99 would have this problem. Something about how they use to build the the ICM/ECM where they just would begin to short after a lot of heat exposure.

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4 years 11 months ago #34592 by Jotmon1
Jotmon1 replied the topic: Re: 99 Grand Am hard start / no start
Seen it before. ECT bad will cause the ECM to go into limp mode on GM V6 of that era cutting out 3 cylinders by killing the spark and fuel. Taking the connector off the ECT will cure the hard start as a test. If that makes it start then replace the sensor.

2003 F150, 2000 Savannah, Chevy 454, 2010 Aveo

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