P0304 Cylinder 4 Misfire Hyundai Elantra: Coil or Spark Plug: How to Diagnose and Fix It Correctly
P0304 on a Hyundai Elantra means the ECM has detected a misfire specifically in cylinder 4, which is most commonly caused by a failed ignition coil (coil-on-plug), a worn or fouled spark plug, or on direct-injection Elantra models, carbon buildup on the intake valve of cylinder 4 disrupting the air-fuel mixture. The coil-swap test: moving […]