Why does the engine miss fire?

The factor leading to engine miss fire is a defective spark plug. This prevents or affects the coil voltage from jumping the electrode gap at the end of the spark plug to ignite the spark. Secondly, the air – fuel mixture might be improper and may not ignite. Thirdly the cylinder might lose most of its air – fuel mixture before it can be ignition. Other reasons may include damaged or broken rocker arms, worn piston rings, valves, cylinder walls, slipped or incorrectly-installed timing belt, leaking intake manifold gasket, defective fuel injectors, etc.