If your vehicle is showing engine misfires or sounds like it is skipping a beat, here are the most likely causes and the parts you'll need to fix each one.
The most common cause of a misfire is spark plugs that are worn out, fouled with carbon, or incorrectly gapped. This prevents the spark from igniting the fuel mixture properly.
Ignition coils provide the high voltage needed for the spark plugs. A weak coil or a cracked rubber boot will cause the spark to arc to the engine block instead of the plug, especially under load.
On vehicles equipped with a distributor or coil pack system, degraded spark plug wires can leak voltage before it reaches the spark plug. Crossing wires during installation is also a common cause of severe misfires.
A failing valve cover gasket or tube seal can allow engine oil to pool around the spark plugs. This oil shorts out the ignition coil or wire, causing a misfire.
A cracked PCV hose or leaking intake manifold gasket lets extra, unmeasured air into the engine, causing a lean misfire. This often happens if hoses are left disconnected after recent engine work.
If a fuel injector is clogged, leaking, or electrically dead, the cylinder will not receive the correct amount of fuel to combust properly.
A burnt exhaust valve, blown head gasket, or worn piston rings can cause a loss of compression in a cylinder, making it physically unable to fire. This is a severe mechanical failure.