camzaro28

after i am driving my car for a while, and i am stopped at a light or whatever, or in traffic the rpm's jump all over. it will start at 750 right when i stop then go to 1500 then drop to 200 then jump back to 2000 then drop to 200, etc, etc. it scares me alot becuz i think the car is going to die on me! and it does this everytime that i have been driving for a while. and also after i let off the gas at say 40 at half throttle and the rpms were at 4000 they would slowly drop to 1500 then stay there with my foot off the pedal. when i am cruising my car is idling at 1500, is that normal? ( and that is with my foot off the gas)
can someone please help me?