Misfire deciding method and misfire deciding system for internal combustion engines

摘要

A misfire deciding method for an internal combustion engine, which can be executed conveniently at low cost by using a gasket type pressure sensor and which can decide a misfire highly accurately and reproducibly. The internal pressure of an internal combustion engine having a spark plug mounted therein is measured by a pressure sensor (or a gasket type pressure sensor) mounted in the mounting seat of the spark plug. The measured information of the internal pressure for a period (or a before top dead center period) after an intake valve is closed and before the crank angle reaches top dead center is used as the before top dead center pressure information, and the measured information of the internal pressure for a period (or an after top dead center period) after the crank angle reaches the top dead center and before an exhaust valve is opened is used as the after top dead center pressure information. Misfire of the internal combustion engine is decided on the basis of misfire decision information obtained using the before top dead center pressure information and the after top dead center pressure information.