If your vehicle is showing engine misfires, jerks, or bucks while driving, here are the most likely causes and the parts you'll need to fix each one.
Over time, spark plug electrodes wear down and the gap widens, making it difficult for the spark to ignite the fuel mixture. This commonly causes the engine to misfire, hesitate, or buck, especially under load.
Ignition coils and spark plug wires degrade from engine heat and age, causing the electrical spark to arc to the engine block instead of reaching the plug. This results in severe jerking and a flashing check engine light during acceleration.
If spark plugs were recently replaced, a cracked ceramic insulator (from improper socket use), an incorrectly set plug gap, or a loose ignition coil connector will cause an immediate misfire. Swapped spark plug wires on older vehicles will also cause violent bucking.
A cracked PCV hose or a leaking intake manifold gasket allows unmeasured air into the engine, creating a lean air-to-fuel ratio. This often causes a rough idle and random misfires at lower speeds.
The MAF sensor measures the amount of air entering the engine so the computer can inject the correct amount of fuel. If it gets dirty or fails, the engine will run poorly, hesitate, and jerk due to an incorrect fuel mixture.
A clogged fuel filter, failing fuel pump, or clogged fuel injectors can starve the engine of fuel when you press the gas pedal. This causes a lean misfire and bucking, usually most noticeable at highway speeds or when climbing hills.
Internal mechanical failures like burnt engine valves, worn piston rings, or a blown head gasket prevent a cylinder from building enough pressure to fire properly. This causes a constant, rhythmic misfire that does not go away with new ignition parts.