I had posted this in the transmissions and drivetrains forum it was suggested by Drew that I try here in this forum. I hope someone can help me figure this out.
I apologize for the length of the posting but I don't want to leave out any information that might help to figure out the problem.
I have a 1985 Firebird L4 (4 cylinder) 2.5L engine. It has an automatic transmission, I'm not sure but I think it is a 700r4. I got the car from the original owner, they let it sit for about 18 months. It started with a jump and test drove fine. The old battery didn't hold a charge got a new battery, the next problem is the car idles fine in park or neutral put in drive or reverse and it would stall out. 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 it to me it was running fine. Within 2 weeks it was running rough or stalling in gear 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 from under the valve cover so we changed the valve cover gasket. Then we couldn't get it to start, another mechanic said from the description it sounded like it had thrown out of time. When I took it to his shop he said that he checked the fuel pressure which was fine & Engine compression which also was fine he then looked for other reasons for the car to not start. It turned out the problem 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 and the mechanic said that it sounded like it was the torque converter locking up. We tried to test by unplugging case connector and ran smooth at first but at high rpms it then drove in gear without stalling. It then started running rough and eventually stalled out in drive. Then it would not start again. I would appreciate any suggestions as to what I might do to figure out the problem. My husband says he has a large sledge hammer, please help me save my 3rd gen Firebird.
Thanks

 

Disconnecting the TCC lockup power was a good diagnostic step. Since it evidently ran without stalling after disconnecting the TCC, there is a good chance that the TCC was indeed engaged. That can be from the clutch itself, or a spool in the transmission sticking and applying the clutch, or an electrical problem causing the clutch to engage when it shouldn't. Since the vehicle apparently sat idle for over a year, and we have no way of knowing whether the transmission has ever had scheduled service, it may be prudent to drain the trans and change the filter, then top off with clean transmission oil. This can help clean sludge and varnish from hydraulic and electrical components and possibly restore proper operation. A reasonably good way to help this along would be to place the car securely on jack stands or a rack and operate the transmission, then apply the brakes while it is in gear to determine if the TCC is releasing.

The stalling and hard starting is likely a different issue altogether. Even though the fuel has been refreshed and filter changed, it would be good to verify proper fuel pressure again. Storage and age can allow a lot of sediment and debris to accumulate in the fuel tank and the new filter may already be restricted (doing its job). You can also observe the pod injector while cranking or running the engine to verify a good spray pattern and no streaming or dripping of fuel.

 

Drew offers excellent advice (as always). If you attempt to clean the IAC it may be better to completely disassemble it and clean the pintle and rack gears in the solenoid core as well, given the age of the vehicle and that it was stored extensively.



This IAC was completely "dead" with only the level of contamination you see above. Simply cleaning and lubricating it (one drop of clean oil) restored operation on this 2.5L TBI.

 

Thanks Vader
We'll try both of these and get back to you letting you know how it works.