The cause of the misfire could be several things, including:
* Spark plug issues: A faulty, worn, or improperly gapped spark plug in cylinder 4.
* Ignition coil problem: A malfunctioning ignition coil for cylinder 4. The coil provides the high voltage to ignite the spark plug.
* Worn or damaged wires: Issues with the spark plug wire leading to cylinder 4. These can be cracked, frayed, or corroded, preventing proper spark delivery.
* Fuel injector problem: A clogged, faulty, or low-pressure fuel injector for cylinder 4 is preventing sufficient fuel delivery.
* Compression issues: Low compression in cylinder 4 due to worn piston rings, a valve problem, or a blown head gasket.
* Vacuum leaks: A vacuum leak in the intake manifold can affect air/fuel mixture delivery to cylinder 4.
* Engine management system issues: Problems with the engine control module (ECM) or other engine sensors (though less likely to cause a misfire in only one cylinder).
To diagnose the problem accurately, you will need a qualified mechanic. They can use diagnostic tools to check the various components listed above and pinpoint the exact cause of the P0304 code. Simply replacing parts randomly is likely to be expensive and ineffective.
