i have had this problem for a while could someone please help me out and tell me whats is going on with my 2000 gt

 

Mine does that if you don't let it warm up...give it a min.

 

How high is your mileage? It could be your Idle Air Control sensor/motor going bad. Mine was acting up, and I replaced it for 40 bucks and now everything is smoot, right at 800 rpms at idle.

 

i got 63,000 mile on it and the car is running at normal temp and it still does it. sometimes at a hard stop then sometimes at a easy stop then some days it wont do it at all

 

You might want to try cleaning the area around the throttle body plate. My car was doing it quite a bit at around 80K. I found that by reving the engine by hand in the engine compartment I found that the plate was sticking a bit. I took the intake hose off, sprayed a rag with carb cleaner and wiped out all the garbage that was making the plate stick. The small ring of buildup you get causes a seal to form and can choke out the motor at idle.

When you're cold, your throttle is more open than when warm so theres is no 'seal'

 

this may sound kinda stupid but is your a/c or heater on because that would cause it.