I have recently acquired a 1985 Firebird L4(4 cylinder) 2.5L engine. It has an automatic transmission, I'm not sure but I think that it is a 700r4 transmission. I got it from the original owner, they let it sit for about 18 months. When we went to check it out it started with a jump and test drove fine. When I got it home the old battery wouldn't hold a charge, when it got a new battery the next problem was that in park or neutral it would idle fine but put in drive or reverse and it stalled. A mechanic friend took a look at it did the rear brakes put in a new thermostat and cleaned the throttle body. When he returned the car to me it was running fine. Within 2 weeks it was running rough or stalling in gear once again. I thought perhaps it was the fuel so we siphoned the tank and changed the fuel filter. Once again it seemed fine. We saw signs of oil leaking under the valve cover so we changed the valve cover gasket. Then we couldn't get it to start, another mechanic said that from the description it sounded like it had been thrown out of time. When I took it to his shop he said that he checked the fuel pressure which was fine and Engine Compression which was fine as well. So he started looking for other causes for it not starting; it turned out is was the ignition rotor. Car ran fine for about a week, once again idling fine in park or neutral, stalling with a thud in drive or reverse. I called the shop that put in the rotor & mechanic said sounded like the torque converter was locking up. Tried to test by unplugging case connector on transmission and ran smooth at first but at high rpms & continued to run in gear. After a short time it started running rough but continued to run in gear it eventually did stall out in drive and would not start again.
I would appreciate any suggestion as to what the problem might be. My husband says he has a large sledge hammer, please help me save my 3rd gen Firebird. Sorry for the long posting but I didn't want to miss anything in case it could help with diagnosis.
Thanks

 

You're going to have a hard time finding anyone on this forum that's done much with a 2.5. It wasn't all that popular to begin with, and there aren't many still around. This might not be the best sub forum to ask either, you might have better luck on the tech / general engine forum.

Any trouble codes?

If you've got an idle problem, 9 times out of 10 it's an IAC related problem. I'd probably start by pulling the IAC, and cleaning the end of the plunger, and the passages in the throttle body with carb cleaner. Depending on how bad it's gummed up you might have to scrub the parts with an old toothbrush.

 

Thanks I will try the other sub-forum. I just came to this one because of the mechanic mentioning the torque convertor and I will check the IAC. Thanks again