The engine computer sees misfires on cylinder 4. The driver usually notices rough idle, shaking and weak power, and the engine light may flash.
Causes vary by car. Test before you order a part.
Likely causes, most common first
- Worn spark plug
- Faulty ignition coil
- Clogged or faulty fuel injector
- Low compression on cylinder 4
Parts usually involved
- Spark plug Find at suppliers
- Ignition coil Find at suppliers
- Fuel injector Find at suppliers
Test before you replace
Swap the coil and plug with another cylinder to see if the misfire follows, then test the injector and compression on cylinder 4.
General guidance for generic OBD2 codes. Always follow the maker's procedure for the car in front of you.