Pontiac Repair: Pontiac Firebird 1990 Engine/Automatic Transmission, pontiac firebird, perfect greetings

Question
G´day

I have got a Pontiac Firebird (1990) with a automatic transmission and v6 3,1 engine.
My problem: when i engage the "D" gear then suddenly the rpm of the engine lowers up to 500rpm/min. After a few seconds the engine brakes down.
Have you got any idea what the problem might be?

Sorry my english is not perfect..:-)

greetings from germany...
Kevin Baierl

Answer
Hi kevin:

How does the car run when cold? does it have the normal fast idle and then slowly idle down as the engine warms up? My first though would be a dirty throttle plate and or idle control motor. I would clean the throttle body and plate and idle control motor. Then diconnect the battery let it sit for a few minutes reconnect the battery. turn the engine to the run position but do not start it let it saty on for 30 seconds. turn the key off for a minute and do the same steps again. Then start the car and let it idle ad see if that fixes it. Good luck :)

P.S. Your english is better then mine!