The engine may not work properly for several reasons and you need to test the car engine to know the real cause of the car engine problem. When the car engine is tested, the engine P1843 Code may come up what gives you some information about the car engine problem. A spark plug helps to move the car. Its purpose is to burn the beaten fuel in the engine. A damaged spark plug will reason a weak spark. It may even stop ignition completely, or reason ignition at the incorrect time. A backfire will touch engine power and fuel consumption and cause massive quantities of possible damage.