I have a 2000 Nissan Altima that's misfiring on cylinder 4 according to a code reader my dad hooked it up to. This is my first vehicle and I know nothing about it. I've gotta get it fixed before winter comes. When I accelerate the car jerks and the check engine light flashes. I've changed the distributed cap, rotary button, plugs and wires, fuel filter, and the alternator is also new. It acts like it's not getting enough gas but runs fine until you get to a hill or go faster than about 40.