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P0308: Misfire detected in cylinder 8

Combustion is failing in cylinder 8. The most common causes are a worn spark plug, a faulty ignition coil or an injector that is not spraying well.

Code P0308 at a glance
CodeP0308
SystemEngine and transmission
GroupP03xx, Ignition and misfires
TypeGeneric: it means the same on every make
Can you keep driving?With care

What P0308 means

The ECU detects each firing stroke through tiny changes in crankshaft speed. It has found that in cylinder 8 the mixture is not burning properly, or at all, and that unburnt fuel goes into the exhaust and overheats the catalytic converter. How the cylinders are numbered is set by each manufacturer.

Most common causes

  • Worn or fouled spark plug in cylinder 8 (on petrol engines)
  • Faulty ignition coil on that cylinder, or a damaged boot or lead
  • Loose or corroded coil or injector connector
  • Dirty, blocked or leaking injector on cylinder 8
  • Air leak near that cylinder (intake gasket or vacuum hose)
  • Low compression in the cylinder from worn valves or piston rings

Symptoms

  • Engine shakes, especially at idle or when accelerating
  • Engine warning light on, or flashing if the misfire is severe
  • Loss of power and jerking
  • Higher fuel use and a fuel smell from the exhaust

Can you drive with P0308?

With care If the light is steady and the engine runs reasonably smoothly, you can drive gently to a workshop. If the light is flashing, stop the car: unburnt fuel can ruin the catalytic converter very quickly.

How to check it

If the engine has one coil per cylinder, swap the cylinder 8 coil with a neighbour, clear the code and test: if the misfire moves, the coil is to blame. Many readers show a live misfire counter for each cylinder.

How to read and clear P0308 with Final OBD

Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0308 with this same explanation and whether it’s confirmed, pending or permanent.

With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.

Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

P0308 is a generic code, so it means the same on any make, for example on BMW, Citroën, Ford, Mercedes-Benz, Renault, Volvo. See what Final OBD does on your car in makes and models.

What does code P0308 mean?

The ECU detects each firing stroke through tiny changes in crankshaft speed. It has found that in cylinder 8 the mixture is not burning properly, or at all, and that unburnt fuel goes into the exhaust and overheats the catalytic converter. How the cylinders are numbered is set by each manufacturer.

Can you drive with P0308?

If the light is steady and the engine runs reasonably smoothly, you can drive gently to a workshop. If the light is flashing, stop the car: unburnt fuel can ruin the catalytic converter very quickly.

How do you clear P0308?

With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0308 comes back.