P0308Powertrain
Powertrain · SAE
Cylinder 8 — Misfire Detected
Meaning
The ECU has detected that cylinder 8 is not producing the expected torque, identifying one or more incomplete combustion events. This is determined by monitoring the angular velocity variations of the crankshaft via the crankshaft/camshaft position sensor.
Common causes
- Defective or worn-out spark plug on cylinder 8
- Faulty or low-efficiency ignition coil
- Clogged or non-functioning injector on cylinder 8
- Loss of compression (burnt valve, worn piston rings)
- Deteriorated or short-circuited high-tension wire
- Head gasket leak between cylinder 8 and the coolant passage
Symptoms
- Check engine light illuminated (flashing in case of severe misfire)
- Vibration and rough engine operation
- Noticeable loss of power
- Increased fuel consumption
- Smell of unburnt fuel from the exhaust
- Possible jerks or hesitation during acceleration
Severity
Grave: Prolonged misfiring can damage the catalytic converter due to overtemperature and cause internal engine damage.
What to do
- Read freeze frame data to identify the conditions at the time of the fault
- Replace the spark plug on cylinder 8 and check the condition of the ignition coil
- Swap the ignition coil of cylinder 8 with that of another cylinder and verify if the code moves
- Measure compression and, if necessary, perform a leak-down test
- Check injector 8 flow rate with a flow tester