Black, dry soot on the electrodes and insulator tip indicates a carbon-fouled plug. This can be caused by a dirty air filter, excessive driving at low speeds, too rich of a fuel/air mixture or idling your vehicle for too long.
What causes carbon fouled sparkplugs?
Causes of carbon fouling include rich fuel mixture, clogged air filter, prolonged low-speed driving or idling, faulty ignition system, retarded ignition timing and spark plug heat rating is too cold.
How do you fix carbon fouled spark plugs?
Can You Clean a Carbon-Fouled Spark Plug?
- Sandblasting – Using a machine that shoots sand out with a jet of air to scrape the carbon off the spark plugs.
- Burning with a butane torch – Some DIY repairers have also shared that it's possible to burn off the excess carbon with a butane torch.
