Patent ID: 7559192

Claim:
An engine control apparatus comprising: a catalyst provided in an exhaust system of an engine, for purifying exhaust gas; various sensors provided in the engine; an operational state calculating means for calculating an operational state including at least an engine rotational speed and a filling efficiency based on outputs from the sensors; a fuel injection amount calculating means for calculating a fuel injection amount of the engine based on the operational state; an injector driving means for driving an injector for injecting fuel into an arbitrary one of cylinders in accordance with the fuel injection amount; an actual misfire ratio calculating means for making a determination on presence/absence of a misfire and calculating an actual misfire ratio based on the outputs from the sensors; a catalyst damage determining misfire ratio calculating means for calculating a misfire determining ratio for making a determination on a damage-causing misfire state in which the catalyst is assumed to be damaged, based on the operational state; a catalyst damaging misfire determining means for comparing the actual misfire ratio with the misfire determining ratio and cutting off a supply of fuel to a misfired one of the cylinders when it is determined that the damage-causing misfire state has arisen; a misfire ratio storing means for storing the actual misfire ratio at a time when it is determined that the damage-causing misfire state has arisen as a misfire ratio at a time of a determination that the damage-causing misfire state has arisen; and a fuel supply cutoff recovery means for outputting a drive permitting signal to the injector driving means to make a recovery from cutoff of a fuel supply when a predetermined condition is satisfied, wherein the fuel supply cutoff recovery means determines that the predetermined condition is satisfied when the misfire determining ratio has become larger than the misfire ratio at the time of the determination that the damage-causing misfire state has arisen.