Spark Plug: Description and Operation

Spark Plugs (Original Equipment NGK Plugs Shown):

Spark plugs provide the path for high secondary ignition system voltage to flow to ground. It is this current, arcing between plug center and ground electrodes, that creates the air/fuel mixture ignition spark. Many spark plugs are made with an internal resistor, designed to reduce ignition system electrical interference with entertainment systems and computerized devices. RX-7 spark plugs operate in the same manner but are specifically designed to function efficiently with the rotary engine.

NOTE: Leading and trailing plugs are not the same. When servicing plugs, use care to ensure that they are installed correctly.

Spark Plug Heat Range Illustrated:

An important consideration when selecting spark plugs is "temperature." Heat range, determined by insulator length and the size of the heatsink area, is defined as the plug's ability to dissipate heat. Generally, a cold plug will be more prone to fouling and a hot plug may cause preignition. Select plugs according to manufacturer recommendation for the type of service a vehicle receives.