Patent attributes
An air-fuel ratio of each cylinder is estimated on the basis of a detection value of an air-fuel ratio sensor disposed in an exhaust confluent portion. An air-fuel ratio correction quantity is computed on the basis of the estimated air-fuel ratio of each cylinder. The air-fuel ratio of an air-fuel mixture to be supplied to each cylinder is corrected on the basis of the cylinder air-fuel ratio correction quantity to reduce a variation in the air-fuel ratio between the cylinders. When a state in which the cylinder air-fuel ratio correction quantity or its learning value of any cylinder is outside a specified range continues for a while during a period in which this cylinder air-fuel ratio control is performed, a combustion is stopped for the cylinder outside the specified range and the cylinder air-fuel ratio control is continuously performed only for other normal cylinders.
