P0300 — Random misfire across multiple cylinders — engine shakes at idle, stumbles under load, loses power, Check Engine light on solid or flashing

What it means

Common causes

• Worn or oil-fouled spark plugs — typical at 30–60K km with cheap plugs
• One or more failing ignition coils — common on VAG, Toyota, Nissan past 100K km
• Vacuum leak: cracked intercooler pipe, PCV valve, split vacuum lines
• Poor cylinder compression — worn rings, burnt valves, stretched timing chain
• Clogged or failing fuel injectors — especially on diesels and GDI engines
• Bad fuel — water, excess ethanol, low octane from a sketchy station
• Clogged exhaust or worn cat — back-pressure disrupts combustion

How to diagnose

1. 01

   Read all stored and pending codes with an OBD-II adapter — get the full picture, not just the one code.

2. 02

   Capture freeze-frame data (RPM, coolant temperature, engine load) at the exact moment the code triggered.

3. 03

   Inspect the named subsystem with our app's AI explanation — get vehicle-specific causes for your make, model and year.

Related codes

• P0301 Misfire in cylinder 1 — engine loses grunt, hesitates under acceleration, shakes at idle, fuel economy worsens
• P0302 Misfire in cylinder 2 — same diagnosis as P0301 but on cylinder 2. Rough running, power loss
• P0303 Misfire in cylinder 3. Consistent engine shake, most noticeable on cold start
• P0304 Misfire in cylinder 4. Often shows up alone on 4-cylinder engines due to uneven plug wear
• P0305 Misfire in cylinder 5. Applies to 5/6/8-cylinder engines (V6, inline-5, V8)
• P0306 Misfire in cylinder 6. On V6 this is the last cylinder — often wears first due to heat exposure