What does code P0303 mean?
P0303 means the engine computer has detected a misfire in cylinder 3: the fuel in that cylinder is not burning properly. The car jerks, shakes at idle and feels down on power.
Why does code P0303 appear?
- Cylinder 3's spark plug is worn or dirty.
- Cylinder 3's ignition coil or plug lead is weak.
- Cylinder 3's injector is clogged or not delivering fuel properly.
- Low compression in this cylinder, for example a valve or head gasket fault. This is less common but costly.
What can you safely check for P0303?
- Note whether the check engine light is steady or flashing, and tell the mechanic.
- Write down every code the scanner shows, not just this one. Do it before clearing them, because the other codes help the mechanic find the real cause faster.
- If the plugs or coils haven't been changed in a long time, tell the mechanic; this is a common cause.
Is it safe to drive with P0303?
If the check engine light is flashing, don't drive fast. Drive gently straight to a mechanic, or stop somewhere safe and call one. In a misfire, unburnt fuel goes into the exhaust and can overheat and ruin the catalytic converter. If the light is on but not flashing, still get it checked this week.
Safety: never remove the radiator cap on a hot engine; boiling coolant can burn you. Keep your hands away from the fan and belts while the engine runs. If you smell fuel, switch off, keep any flame or cigarette away and call a mechanic.
When should you call a mechanic?
If P0303 appears, have a car mechanic (mistri) check it soon. They will test whether the cause is cylinder 3's plug, coil, injector or compression. Testing costs less than swapping parts by guesswork.