P0304 – Cylinder 4 Misfire Detected
Description
The engine control module detects a misfire in cylinder 4, which affects engine smoothness and may damage the catalytic converter.
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A diagnostic scanner with live data, freeze-frame information and the right system access can help you investigate the actual cause before replacing parts.
Compare Diagnostic ScannersSymptoms
- Rough idle
- Loss of power
- Check engine light flashing under load
- Fuel smell from exhaust
Causes
- Faulty spark plug
- Ignition coil failure
- Fuel injector malfunction
- Mechanical issue in cylinder 4
Diagnosis
- Check misfire counters and freeze frame data
- Swap coils and spark plugs between cylinders
- Perform compression or leak‑down test
- Check injector operation
Repair
- Replace spark plug or ignition coil
- Clean or replace the injector
- Repair mechanical faults
- Clear codes and perform a load test
