Its come to my attention that the car is running strang when i start it up the rpm's seem to jump 500-650(guess) back and forth if i put it in gear and give it gas they do the same thing no matter if im at 1500 or 2500RPM(does not shack the car only rpm's shift) less then a min it will be fine its not all the time theres no pattern i can see of when or why it dose this please help