I have a 92' GTA TransAm. I have a recent issue with it and can't seem to pin point the actual problem. I have changed everything from sensors to a complete tune up and even did the exhaust and still, the car wants to idle erratic and stall, Flashes engine light and no code is stored on ECM.
I was able to get it down to a very local mechanic and have a diagnostic ran on it, he says it's believed to be a short in the wiring and offers a fix for 650. Thing is, everyone I talk to say's to try this, try that and some think the guy is trying to rip me off.
Though I did remove the recent stereo that I installed back in October and oddly enough the car ran better and started right up with no problem. If it was a "fluke" I don't know. I haven't taken it out on the street yet, in case it breaks down. I wanted to get some advice and answers first. I know there was obviously a wiring problem at some point, when I bought the car. I noticed were some heating had taken place and been replaced. It's not coming from the same area again.
If this is a wiring deal, would that cause the power window's to be erratic and delayed in going up and down? Possibly cause the horn to not work? And maybe even cause the power sets to not work?
My biggest concern, obviously, is to fix the problem so it runs excellent again. The car is in over all outstanding condition, no other problems what so ever. It's just this mystery and pin pointing the exact problem. Any help or advice would be appreciated.
Thanks!!

 

What size alternator are you running in it?

 

The alternator is a 105amp and is told to be compatible with the car. Though it's interesting too, I just replaced the alternator a year ago or less and when I took it out a couple weeks ago to find this problem, I had it tested and they said it was weaker than it should have been. So they exchanged it for another new one. What would make the first new one become weak so quick is a question as well.