When I'm coasting along in gear and just letting the car pull itself when I go on the throttle lightly the revs drop and go back to normal which is causing a jolting motion. When the engine is running and I'm stationary and tap the throttle a little the revs drop also? When I'm driving and want to stay at a speed limit, I have to be on the throttle or off it there's no in between? PLEASE HELP ITS DRIVING ME CRAZY