Patent ID: 8010278

Claim:
A control apparatus for an internal combustion engine comprising: an alcohol concentration estimation means that estimates an alcohol concentration value ALC 2 for the engine that utilizes an alcohol-containing fuel; a storage means that stores the alcohol concentration value ALC 2 estimated by the alcohol concentration estimation means; an alcohol concentration feeding means that forcibly and tentatively changes an alcohol concentration value; a feedback interruption means that interrupts feedback control in engine control when the alcohol concentration feeding means forcibly and tentatively changes an alcohol concentration value; a determination means that determines whether or not to replace the estimated alcohol concentration value ALC 2 stored in the storage means by the tentatively changed alcohol concentration value ALC 1 ; and an update means that replaces the alcohol concentration value ALC 2 stored in the storage means by the tentatively changed alcohol concentration value ALC 1 , when the determination means determines to implement the replacement.