P0301

• Check engine light on or flashing (flashing means serious!)
• Engine shaking, stumbling, loss of power
• Rough idle
• Noticeably higher fuel consumption
• Smell of unburnt fuel from the exhaust

• Worn or oil-fouled spark plugs
• Ignition coil failure
• Crankshaft / camshaft position sensor problem
• Faulty injector or low fuel pressure
• Low compression in a cylinder (mechanical problem)

1. Use an OBD-II scanner to find which cylinder is misfiring (read the misfire counters).
2. Remove the spark plugs and check for wear, carbon and oil fouling. Measure the plug gap.
3. Swap the ignition coils between cylinders and see whether the misfire moves to another cylinder.
4. Check the crankshaft position sensor signal with an oscilloscope or multimeter.
5. Do a compression test to assess the cylinders' mechanical health.

1. Replace worn spark plugs with the correct type (only at the recommended gap).
2. Replace the faulty ignition coil — ideally renew all coils at the same time.
3. Replace the crankshaft or camshaft sensor if it is faulty.
4. If compression is low, further diagnosis is needed for the head gasket, valves or piston rings.
5. Clear the code and road-test at idle and under load to confirm the fix.

• Kia: Cylinder 1 Misfire Detected

• P0300Random/Multiple Cylinder Misfire Detected
• P0302Cylinder 2 Misfire Detected
• P0303Cylinder 3 Misfire Detected
• P0304Cylinder 4 Misfire Detected
• P0305Cylinder 5 Misfire Detected
• P0306Cylinder 6 Misfire Detected

This page is general information; an exact diagnosis needs measurements and a technician’s check.