Help !!!! have moisture issues

[tonys1228]

95 pontiac grand prix

clue #1
car wont run more than 1 min when it is damp and rainy out. After it gets hot it wont run at all untill the air gets dry again, then starts and runs great untill the next rainy weather. Ive checked and ruled out the battery, altenator, ECM(power pak under the coils) and checked the fuses.

other clues.....
When the above started these below all started the same time.
THe speedometer and tach quit working. The oil, temp, and other idiot lights dont work and therefore cannot get a diagnostic signal from them. Finally when you turn on the headlights the warning bell sounds until you turn the lights back off.

I dont know what do check next other than the computer.... HELP please I need this car running badly....

Tony

[richtazz]

Welcome to AF.

Since it's a dampness related issue, I would first check the condition of the ECM (Emission Control Module). (The ICM [Ignition Control Module] is the part under the coils you said you checked and called the ECM). The ECM is mounted under the hood in the right front fender well area, and are known to have moisture intrusion issues. All of the systems you are having issues with are controlled by the ECM, so that's the first thing you need to look at.

[tonys1228]

Thanks for pointing out that it was the ICM and not the ECM... Is the ECM also called the "computer" ? I think I read somewhere it is located directly behind the headlamp on the passenger side. How do I test it and waterproof it or do i just replace it?

Thanks ,
Tony

[richtazz]

Yes, the ECM is also called the computer. It is located under the plastic cover on the passenger side, between the wheel well and headlamp. You can try a tap test to see if you can get it to act up. Take the handle of a screwdriver, and gently tap on the top of the ECM while the car is running and warmed up. If the car stumbles while you're tapping, the ECM is bad. You can also visually inspect it to see if you notice excessive rust on the outer case, or signs of corrosion (the green nasty powdery stuff) on any of the wiring harnesses. Lastly, if the GM service number on it is 1227727, that is a part number with a high failure rate.

[tonys1228]

Ok, thank you for the info.
Im going to try tapping and take a close look at it.