Misfire Monitoring Description

The method of engine misfire detection is based on evaluating the engine speed fluctuations. In order to detect misfiring at any cylinder the torque of each cylinder is evaluated by metering the time between two ignition events, which is a measure for the mean value of the speed of this angular segment. This means, a change of the engine torque results in a change of the engine speed.

Additionally the influence of the load torque will be determined. This means the influences of different road surfaces, e.g. pavement, pot holes etc. If the mean engine speed is to be measured, influences caused by road surfaces have to be eliminated. This method consists of the following main parts:

• Data acquisition, adaptation of sensor wheel is included.
• Calculation of engine roughness.
• Comparison with a threshold depending on operating points.
• Some extreme conditions, during which misfire detections should be disabled for a short time.
• Fault processing, counting procedure of single misfire events.