Symptoms drivers describe
- Shaking or vibration, often worst at idle
- Hesitation or a stumble under acceleration
- Engine light on, or flashing in more serious cases
- Poor economy and a smell of unburnt fuel
- Uneven exhaust note
Possible causes
- Ignition coil or spark plug failure on petrol engines
- Injector wear, blockage or leakage
- Air leaks after the air-mass sensor
- Low compression from valve or piston ring wear
- Timing faults, including a stretched chain
- Wiring or connector faults at the coil or injector
What you can do
- Stop driving if the engine light is flashing
- Note whether it misfires cold, hot, at idle or under load
- Avoid replacing plugs and coils speculatively before testing
How we check it in the workshop
We read misfire counters per cylinder, then test spark, injector operation and compression on the affected cylinder so the repair addresses the actual cause.
Is it safe to keep driving?
Prompt. A persistent misfire wastes fuel and can damage the catalytic converter.