Abstract: Spark plugs in an internal combustion engine may have an encapsulated spark gap allowing for improved emissions and efficiency. However, increased temperatures in an ignition chamber about the spark gap may cause pre-ignition of a air fuel mixture in a combustion chamber. A purge passage allows hot exhaust gas to be expelled from the ignition chamber and thus reduce likelihood of pre-ignition.

Abstract: A system for monitoring the exhaust gas hydrocarbon content of an internal combustion engine includes at least one sensing device for detecting whether expected combustion conditions occur within the combustion chambers and responsively producing signals indicative of whether the expected combustion conditions occur. An electronic controller is connected to the at least one sensing device for receiving signals therefrom, the electronic controller being operable to determine an estimated exhaust gas hydrocarbon content based upon the signals received from the at least one sensing device. In particular, an engine misfire rate may be determined by the electronic controller and the estimated exhaust gas hydrocarbon content may then be determined as a function of at least the determined engine misfire rate.