Misfiring detection

The smooth-running values of the individual cylinders are indicated for troubleshooting purposes. The engine must run at idle speed for at least 3 minutes to ensure that the useful values are set. Smooth idle speed can only be evaluated with the engine running at idle speed (cold or hot). An individual cylinder with poor combustion is detected exactly. Random fluctuations in the smooth-running value of an individual cylinder can only be detected by close observation of the value. In the case of an engine with theoretically even combustion, the smooth-running values are 0 (averaged over all cylinders). An increase in the smooth-running values may be caused by various factors (e.g. misfiring, excess air, mixture deviations, faults in fuel supply system, low compression). For this reason, exact control limits cannot be specified. The crankshaft sensor is used to measure the engine speed at the increment gear. In addition to the engine speed detection, the smooth running of the engine (= misfire detection) is also monitored. For misfire detection, the increment gear in the DME control module is divided into 2 segments according to the firing interval (between 2 ignition operations). Within the DME control module, the periodic duration of the individual segments is measured and statistically evaluated. For each mapped value on the characteristic map, the maximum permissible values for irregular running are stored (as a function of engine speed, load and engine temperature). If these values are exceeded for a certain number of combustions, a fault memory entry is stored for a cylinder regarded as faulty.