A control for an internal combustion engine in which it is determined whether a request for a turbo flow mode is output and whether there is a possibility that a catalyst may be deactivated. More specifically, it is determined whether a catalyst gas temperature is above a predetermined value. The predetermined value is set in advance so that when the catalyst gas temperature is equal to or below the predetermined value, the catalyst is deactivated. When it is determined that there is a possibility that the catalyst may be deactivated if exhaust valves are placed in the turbo flow mode, a retard amount in an ignition timing retard correction is determined. An ignition timing is calculated. It is permitted to switch a valve opening mode to the turbo flow mode.