Dry, Fluffy Black Deposits - Cold or Carbon Fouling

COLD FOULING (CARBON FOULING)

Normal Operation And Cold(Carbon) Fouling:

Cold fouling is sometimes referred to as carbon fouling because the deposits that cause cold fouling are basically carbon. A dry, black deposit on one or two plugs in a set may be caused by sticking valves or misfire conditions. Cold (carbon) fouling of the entire set may be caused by a clogged air cleaner or poor ignition output.

Cold fouling is normal after short operating periods. The spark plugs do not reach a high enough operating temperature during short operating periods. Replace carbon fouled plugs with new spark plugs.