I own a 1986 IROC 305tpi f/i a/t. My mechanic can't even seem to figure out the electrical problems I have had with it. To begin, for the longest time I have had a really slow drain on the battery that will take 3 days minimum to full drain it, sometimes up to a week. Lately though I have run into a lot of problems with the computer. Sometimes I will crank the car and it will idle a little rough and the service engine soon light will come on. When I give it gas, the engine will idle down to around 300 rpms and then cut off. Sometimes this will happen even when the service engine soon light does not come on. Usually, this happens after I have run the car for a couple mins then cut it off and try to start it within the next hour. Today while at my mechanics shop he figured it was the ECM by starting the car and banging on the dash. When he did this it immediately cut off the car. He then took out the ecm from its position under the passenger dash and laid it in the floor still hooked up and cranked the car. When he tapped directly on the ECM the car shut off, but while shuffling through the wires, the car continued to run.


Any ideas as to how I can manage to kill the stock computer and then kill this computer 2 months later? Also, when the service engine soon light would come on the diagnostic computer and 2 prong key both failed to produce anything. It would either say the diagnostic computer was not hooked up or the light would not flash the 1-2 1-2 1-2.


Another electrical problem I am having that is somehow linked deals with my cooling system. When I start the car the gauge will go up depending on the temperature (I assume it works fine the first time), but when I turn it off and recrank the car the temperature gauge will read random numbers, usually 100 degrees. This can be done after the car has been running at in 90+ temperatures in stop-n-go traffic for a decent time, and it will still reset the gauge to 100 if I turn off the car and turn it back on. This I feel is somehow linked though because the problem with the computer seems to be most prominent when the fan does not cut off even when the car is cooled off if the key is in the ACC.


Any ideas, because my mechanic thinks it is a ground problem, but still can not explain why the computers both got shot so fast.




To help diagnose any problems on why the battery is draining I'm listing the only mods I have made to the car:
-Pioneer CD Player
-Aftermarket replacement power antenna
-Aftermarket alarm system with remote start/trunk release/keyless entry (installed by Best Buy and surprisingly has no visible flaws in wires or wiring)[when I took the car to them to try to find out if the drain was caused by the alarm, the guy helping me showed no ampheres on the meter and showed the battery recovering voltage and not losing while there and turned off]

Feel free to leave a response, any suggestions/ideas or e-mail me as I would love to try to solve this problem that has kept her out of commission for 3 weeks already.

 

Maybe this could be a bad driver? Know if you have any shorted injectors or anything?

 

I found this on Chevythunder.com

"NOTE: DON'T BURN UP YOUR ECM'S!!

Be sure to check the resistance of all your relays and solenoids BEFORE you start your tpi for the first time.

IAC, EGR, air select, air diverter and canister purge solenoids should read at least 20 ohms with a digital meter.

The fuel injectors should be at least 10 ohms , with the normal range around 12-16 ohms.

The relays such as MAF, MAF burnoff, fuel pump, cooling fan etc., should read between 40-60 ohms, no less than 20 ohms.

If the resistance values are too low, the excess current through the ecm's driver circuits will destroy it in a short time. This also goes for carefully checking the wiring harness for shorts."

I do remember a story like this, where some guy had a blown ecm and instead of the mechanic looking for the reason as to why it was blown, he just replaced it and the car came back sometime later with another blown ecm. My memory is fuzzy, but I think it turned out to be the driver. Either that or it was injectors that had shorted due to a bad driver. Anyway, make sure this mechanic isn't just a parts swapper and will actually find the problem.

 

He has checked all the relays, and the car has 40k miles on it, and is driven mostly on the highway to and from school when I don't drive my truck.

 

Where did the replacement ecm come from? G.M. computers from the 80's have solder joint problems that cause the ecm not to work properly. If the replacement was used or rebuilt by a questionable rebuilder it may have had the same problem.

 

It came from Carquest, and I think was a replacement part not a rebuilt one.

 

I don't think Carquest sells replacement computers just reman's. The tap test on the ECM show's bad connections internal to the ECM. I once worked on a late 80's or early 90's cavalier that would randomly cut out while driving it took me three day's of on and off driving the car for it to finally cut out on me. The problem was the ecm would have problems with the vehicle speed input and display random numbers in the scan data some of them where over the high speed cutout point and shut off the fuel. So the ECM you got from Carquest may have tested fine at the Reman shop and got shipped backout without any repairs. Send it back for a warranty one or try one from ACdelco.

 

It was a remanufactured one, but I figured out what all the problems were caused by. The oil pressure in my car was dropping when the engine was warm because I have a leak in my head or head gasket causing the oil to get watered down lowering viscosity. Also this gave me a bad reading on my temp gauge as it would get low enough to read the air in the radiator and not the water. This in turn caused my car to produce too much heat for the cpu and to cause it to overheat and melt solder joints. Now I have to replace either the heads or the gaskets, not sure which as I just found out the cause of my problem today while talking to some fellow students in my engineering class about my problems with my car.

 

wat? isnt the ecu inside the cabin? that shouldnt affect it, carquest is knowen for cheap parts.