P0300
High severityRandom / Multiple Cylinder Misfire Detected
Quick answer
P0300 (Random / Multiple Cylinder Misfire Detected) means: The engine is misfiring across multiple cylinders, which can damage the catalytic converter. Address promptly; a flashing light means stop driving and seek help. Typical Malaysia repair cost: RM200–RM800 (approximate).
Symptoms
- •Shaking/rough idle
- •Loss of power
- •Flashing check engine light
Likely causes
- •Worn spark plugs/coils
- •Vacuum leak
- •Fuel delivery problem
- •Low compression
Can I drive?
Address promptly; a flashing light means stop driving and seek help.
Estimated repair cost (Malaysia)
RM200–RM800 (approximate)
Diagnostic guide (for mechanics)
Work through these in order — cheapest and safest checks first, before replacing expensive parts.
1. Read misfire counters per cylinder
Use live data misfire counts to see whether it is truly random or concentrated on certain cylinders. A pattern points to a specific coil/plug/injector.
2. Inspect spark plugs and coils
Pull and inspect plugs for wear, fouling, or wrong gap. Swap a coil to an adjacent cylinder and re-scan to see if the misfire follows.
Test: Coil primary resistance with a multimeter (compare against a known-good coil).
Expected: Coils read consistent with each other; plugs gapped to spec and not oil/fuel fouled.
3. Check for vacuum/intake leaks
A lean condition from an intake leak causes random misfire. Inspect hoses and the intake boot; watch fuel trims.
Test: Live data long-term fuel trim at idle.
Expected: Fuel trims within roughly ±10%.
4. Test fuel delivery and compression
If ignition and air are good, check fuel pressure and do a compression test on the affected cylinders.
Test: Fuel pressure gauge; compression tester.
Expected: Fuel pressure to spec; compression even across cylinders (within ~10%).
Tools: OBD-II scan tool · Multimeter · Spark-plug socket · Compression tester · Fuel-pressure gauge
When to escalate: A flashing check-engine light means stop driving — continued misfire can destroy the catalytic converter. Refer low-compression findings for internal engine work.
This is general information, not a diagnosis. AutoMalaya OBD helps explain your car’s actual scan data; a qualified mechanic may still need to inspect the vehicle.