Temperature sensor for internal combustion engine

A misfire in a combustion chamber of an internal combustion engine is detected by measuring a combustion chamber temperature with a temperature sensor element without using a pressure sensor having a low heat-resistive property. A temperature sensor includes an elongated probe portion extending from a housing. The housing is mounted on an engine so that the probe portion is exposed to the combustion chamber. A diaphragm is disposed on a tip of the probe portion, and a sensor element such as a thin film thermistor is mounted on the diaphragm, preferably on a rear surface of the diaphragm where the sensor element is not directly exposed to mixture gas in the combustion chamber. The sensor element may be embedded in the diaphragm. The probe portion of the temperature sensor may be integrally formed in a spark plug thereby to save a space for mounting the temperature sensor on the engine.