My car shakes and jerks and it gives a code that says there's a misfire in cyl 3 but sometimes this doesn't happen and it works just fine. I've replaced the spark plugs wires coil pack fuel and oil filters and still no luck. Still I'm stumped as to why some times I'll start the car the mil light will be on but it will be fine and other times it will blink and the car will **** and run at half power and other times the mil light goes out and it runs like a good car should. Plz help I don't have a lot of money and im trying to sell it fast. Plz help the codes it's giving when it acts up are p0300 and p0303 but again it doesnt happen all the time.