I bought a 1995 ford ranger back in february and the only major problem with it I have it with now is that the engine is shaky when its idle or really shakes when im going a certain speed...which is usually around 35 mph or so....its 6cyl 4l and im not sure what it could be...i know when i took it to the machanic he said that cylinder one was backfiring...any ideas on how to fix this problem without going deep into spending money or what it might be?