Firing state discrimination system for internal combustion engines

摘要

A firing or ignition state discrimination system for an internal combustion engines having a spark plug which produces spark discharge when supplied with discharge current from an ignition coil to ignite air-fuel mixture in the combustion chamber. In the system, ionic-current that flows during combustion of the air-fuel mixture is detected at a predetermined first timing and leakage current that flows across electrodes of the spark plug is detected at a predetermined second timing which is later than the predetermined first timing. The firing or ignition state of the engine is discriminated to one from among normal, misfiring, spark plug fouling, and failure in ignition system or in fuel supply system based on the detected ionic-current and leakage current and presence or absence of fuel cutoff to the engine. With this, it becomes possible to accurately discriminates the firing or ignition state of the spark plug and to inform the fact to the vehicle operator if desired.