P0300 – Random/Multiple Cylinder Misfire Detected
Generic powertrain code indicating that the ECU has detected misfires on more than one cylinder.
Plain‑English Explanation
Your engine control unit is seeing irregular crankshaft acceleration between firing events, which indicates that one or more cylinders are not contributing power reliably. Because the pattern is not tied to a single cylinder, it is logged as a random/multiple misfire.
Common Symptoms
- Check engine light flashing or steady.
- Rough idle, especially when cold.
- Hesitation or jerking under load.
- Increased fuel consumption.
- In severe cases, smell of unburnt fuel from the exhaust.
Typical Causes
- Worn or faulty spark plugs.
- Failing ignition coils or leads.
- Fuel delivery issues (weak pump, clogged injectors, dirty filter).
- Air leaks (intake manifold, PCV system, boost pipes on turbo cars).
- Low compression due to mechanical issues.
What To Check First
- Check freeze‑frame data to see RPM/load when the code was stored.
- Inspect spark plugs and coils; replace if worn, cracked or oil‑contaminated.
- Look for obvious intake/boost leaks and split hoses.
- Use live data or a fuel pressure gauge to confirm fuel delivery is healthy.
- If misfire is severe or persistent, perform a compression test.
P0300 on Ford Fiesta ST (1.6 EcoBoost)
For the 1.6 EcoBoost, misfires are often caused by tired spark plugs and coils, especially on tuned cars or those run on poor fuel. Oil in the plug wells, incorrect plug gaps or mismatched plugs after DIY work are common. If P0300 appears with cylinder-specific misfire codes (P0301–P0304), always inspect that cylinder first.
P0300 on VW/Audi 2.0 TSI/TFSI Engines
On VAG 2.0 TSI/TFSI engines such as the Mk6 Golf GTI, random misfires are often linked to ageing coil packs, spark plug wear or carbon build-up on intake valves. If you see P0300 with cylinder-specific misfire codes, prioritise checking plugs and coils on the affected cylinders, then consider intake cleaning if misfires persist.