Low Data Rate System

The LDR misfire monitor uses a low data rate crankshaft position signal, one position reference signal at 10 degrees before top dead center (BTDC) for each cylinder event. The PCM calculates the crankshaft rotational velocity for each cylinder from this crankshaft position signal. The acceleration for each cylinder can then be calculated using successive velocity values. The changes in overall engine RPM are removed by subtracting the median engine acceleration over a complete engine cycle. The resulting deviant cylinder acceleration values are used in evaluating misfire in generic misfire processing.