Signs of bad spark plugs include the following main symptoms:
- Check engine light turns on. Faulty spark plugs can trigger the engine warning light.
- Engine misfires or stutters, especially under acceleration.
- Difficulty starting the car, with extended crank time or stalling after startup.
- Rough idling or engine vibrations when the car is stationary.
- Poor fuel economy due to inefficient combustion.
- Loss of engine power or sluggish acceleration.
- Black soot or carbon buildup visible on the spark plugs.
- Worn or melted electrodes on the spark plug tip.
- Cracked ceramic insulator on the spark plug.
- Oily deposits on the plug, indicating possible oil leakage inside the engine.
These symptoms indicate the spark plugs are not firing properly and impacting engine performance, fuel efficiency, and emissions. Prompt replacement is recommended to avoid further engine damage and maintain smooth performance.
