Abstract
This paper presents the method to monitor the engine misfire as a part of the OBDII requirements. Engine misfire is described by the engine roughness. The engine roughness is calculated by integrating the pressure torque from the instantaneous angular velocity of each combustion stroke and the integral of pressure torque is compared with the integral of the motoring torque corresponding to the intake manifold pressure. Additionally, the speed waveforms are measured both at the flywheel and the front end. The flywheel speed waveform shows better result than the front end one. This method proves to be efficient in monitoring the engine misfire and in identifying the specific cylinder or cylinders experiencing the single or continuous misfire.