Method for detecting combustion misses

An electronic diagnostic apparatus for detecting combustion misfires in an internal combustion engine which runs rough in response to said combustion misfires, the apparatus comprising:

• means for forming an index for the rough running of the engine;
• means for comparing said index to a threshold value, which is dependent upon the load of the engine, with exceeding said threshold value being evaluated as a misfire;
• and,
• means for providing at least one of the following:
• (a) forming the threshold value in addition to the dependency upon load also in dependence upon at least one of the following:
• the ignition angle and the composition of the air/fuel mixture of the engine;
• (b) designing the formation of the index for the rough running also in dependence upon at least one of the ignition angle and the composition of the air/fuel mixture;
• (c) designing an activation or deactivation of the misfire detection at least in dependence upon at least one of the ignition angle and the composition of the air/fuel mixture of the engine.