Cylinder 3 Misfire Detected

Possible causes

• CommonWorn or fouled spark plug on cylinder 3
• CommonFailed ignition coil on cylinder 3
• PossibleFaulty or clogged fuel injector on cylinder 3
• PossibleBroken or chafed wiring to the coil or injector on cylinder 3
• PossibleVacuum leak local to cylinder 3, for example a cracked intake runner
• RareLow compression on cylinder 3 - burnt valve, worn rings or head gasket

What you might notice

• Engine shakes, most noticeable at idle
• Noticeable loss of power
• Check engine light on, sometimes flashing
• Smell of unburnt fuel from the exhaust
• Rough running that may smooth out at higher engine speed

What to check, in order

1. Swap the ignition coil from cylinder 3 with one from a neighbouring cylinder, clear the code and drive. If the misfire follows the coil to the other cylinder, the coil is the fault. Only do this if your engine uses interchangeable coil-on-plug units.
2. Inspect the spark plug from cylinder 3. Compare it against the others - oil fouling, heavy carbon or a cracked insulator all tell you something.
3. If the misfire stays with cylinder 3 after swapping the coil and plug, suspect the injector or compression.
4. Check the connector and wiring at the coil and injector for cylinder 3. Chafed insulation and green corrosion are common.
5. A compression test on cylinder 3 is the last step - it distinguishes a mechanical problem from an electrical one.
6. If the check engine light is FLASHING, stop driving and have the car recovered. A severe misfire can destroy the catalytic converter within minutes.