Hi When i start my scoupe.. it starts with a fumble a vibration. Also if i stop at a stop light and i hit the brakes, the engine goes down to like 400 rpm and goes up back to 900 . Most of the times when i stop the engine vibrates, the steering wheel and i just did a oil change, i changed plugs almost a yr ago, i never changed gas filter, I changed plug wire the same time i changed spark plugs. I didnt changed distributor cap and rotor... engine have 186000km on it, if there is any help what shoud i do, it is greatly appreciated...