Quote Originally Posted by mark97564 View Post
It's an old car, how did you check compression? Did you hold the throttle to the floor? What's the numbers? I added compression to the list of what could be wrong with your car because some people don't know how to check it properly, but I did see you say you did.. also beleive it or not in my 2005 comp g I had a misfire the pcm didn't even detect, I'm just ocd like that and it turned out to be the maf on my gtp .. and the series 1 and series 2 are well known for maf issues. So bad actually that after market ones come bad in the box time and time again..

Also, when the light comes on do you feel a misfire? If I can detect a miss the pcm can't then I would like to know if the car is actually misfiring? For it to set a check engine light it would have to be pretty noticable. And if it does misfire does it do it so bad the cel starts flashing? There are 2 stages of misfires.. small ones the pcm sets a code for and bad ones that actually get the light to start flashing..

I know these cars well so I can help.. if you have a 2 channel oscilloscope it would help in diagnosing a faulty icm... Also some part stores can check them. And the ground wires for the icm and coils are right on the icm bracket and could be corroded and crappy
I have replaced maf sensor already, it made no change. I have not checked the grounds. I have not messed with crank sensor at all. The CEL does not flash and there is no noticeable drivability issues, as long as I dont let the car idle for more than 10 to 20 min. The light never comes on, so whatever is causing it would appear to be an idle condition. For the compression test I just used your run of the mill Matco tester I tested throttle wide open, I know you get lower numbers if you dont. I also tested with and without a little bit of oil to see if there was any loss from the rings. Compression from #1 to #6 accordingly...142, 136, 140,140, 142,138. I'd also like to add I've replaced the pcm as well so we can eliminate that I'm thinking at this point I need a camera so I can look in there and see what's happening. I dont know if it's relevant but I could start this car and drive across the United states and the light will not come on, but if I go in the gas station and leave it running idle for a little the light will be on lol. Otherwise the car drives great, no power loss or hesitation, no rough idle, averages 20mpg , no spark knock of any kind. I've owned this car for 3 years and it has always been the same before and after the light.