What is spark plug fouling?
Spark plug fouling is a phenomenon by which carbon accumulated at the firing end causes electrical leakage that leads to mis-firing. As the voltage generated by the ignition coil leaks away through the carbon, mis-firing may occur and cause running and staring difficulties. As carbon builds up, the insulation resistance of the spark plug drops and the voltage generated by the ignition coil is reduced. When the generated voltage becomes lower than the required voltage of the spark plug (the voltage needed to cause sparks at the spark gap), sparking is suppressed and mis-firing occurs.
