PURPOSE: To recognize erratic combustion precisely even under abnormal operation conditions of a multi-cylinder internal combustion engine by processing a static component and a timing component considering the entire speed tendency as well as an additional speed change component.
CONSTITUTION: A predetermined time interval Tn is measured (S1) using markings on a crankshaft KW. After intermediately storing (S2) the measured value, a normal factor NO is used to calculate (S3) a static component LUSn. A timing component LUDn is calculated (S4). After a change component LUKn is calculated (S5), it is intermediately stored (S6) and float averaged (S7). Then, a lack of smoothness value is calculated (S8), and operation parameters of an internal combustion engine are measured (S9). A limit value LUGn of the lack of smoothness value is taken out (S10). It is intermediately stored (S11). Then, the lack of smoothness value LUn is compared with the limit value LUGn thereof (S12). Erratic combustion is recognized (S13) on the basis of the result of the comparison.
MANFUREETO BUIIA
TOOMASU FUOOKUTO
