I'm considering buying the car, He wants $3k. It has 155k miles and a good carfax. I cant tell if the car is misfiring or if the transmission is starting to go out. RPMs jump up and down and the whole car shakes a bit. It does this accelerating at half throttle and while cruising at highway speeds. The owner thinks its a bad ignition coil but I'm leaning towards it being the transmission. The car idles rough and hesitates a bit getting on the gas. Video of whats wrong, headphones recommended