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HELP! 95 grand prix 3100 wtf?


jmatt07

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im completely out of ideas. i even took it to a mechanic and he doesnt know. i have checked about everything i can think of. the problem is when its cold it wont start on its own unless you feather the gas then you have to keep on the gas until the CES light comes on and then it will idle on its own and other times there will be no CES light and it will idle on its own. also the security light is on. we drove it from illinois to ohio and it runs perfect on the highway. its just you cant let it idle. the mechanic bypassed the security system bc he thought it might be causing it but it didnt help. i checked the coils, ignition module, plugs, wires. iac, checked all the grounds. the mechanic did a diagnostic on it and it came up the map sensor but he put a new one in and still same problem, he checked the wiring and said it was fine. this car also runs pretty hot, the fans dont come on till about 230-240 then will come back down to 210. the mechanic says the ignition is worn and can take the key out with the car still runing but i dont see how that would cause the problem. i dont want to keep payin a bunch of money for a mechanic to fix things he just think might be it. does anyone have any ideas or had the same problem and could give me any help? thanks...john

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I think you've hit the "I'm on my own point" meaning your car shouldn't go to the shop except for tires and mufflers. Many shops don't remember how to fix it anymore.

 

See if you can go to the junkyard and grab a junkyard PCM (~$40 if they're an expensive yard). That's my guess. Did you have the ICM tested at an autoparts store? I was leery of that test, but I actually brought a broken and working one side by side, and the machine recognized the broken one.

 

If you're at the yard, grab an extra IAC just for the heck of it. It probably isn't your problem, but its worth a shot

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Egr sticking open?

 

Good call, I hadn't thought of that one... definately check that!

 

Other than that, I'll second that it could be the PCM. Don't write off the fact that the MAP code could be correct... check all the wiring and vacuum lines going to the map sensor. If any of them are damaged, they could cause the code your mechanic saw. I know from experience that problems with either of those can cause problems very similar to what you describe

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i have seen a couple times with it running hot it may be the coolant temp sensor(cts) or a nasty vacuum leak.

 

may also be your coils that might show good but not a strong enough spark you can pick them up cheap at a yard and try swapping for gits and shiggles

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If the security light is one could it be the vats chipped key crap?

 

Check the vac lines. If you have a spare key...try it. You'll know if it's VATS if you have another key and the problem goes away.

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