The best way to clean the spark plug is by sand blasting. You can follow these easy steps – first of all remove your spark plug using a torque wrench with correct torque value. Keep in mind the wiring connections – they should be arranged in a similar manner after cleaning. Use a soft cleaning cloth / brush and clean the spark plug of any dust. A wire brush can be used to clean the threaded part. Using carburetor / brake cleaner or mineral spirit (most preferred) clean the firing end. Hydrogen chloride solution (about 20 %) (Muriatic Acid ) can also be used, but be careful – it is highly acidic and harmful. After this, rinse the spark plugs well using alcohol, carburetor / brake cleaner or mineral spirit and dry it out thoroughly well. Use pressurized air to clean the spark plugs. Use a dry compound to clean any excess deposits invisible to naked eyes and once again air blast the spark plug, and finally put your spark plug back in place!