To prevent an increase in torque when the fixed state of a throttle valve is released. When diagnostics reads fixed diagnostics flag 1 indicating that the throttle valve is in a fixed state, control value ATVO that can maintain throttle aperture RTVO is set (S11, S12) based on detected value RTVO for the throttle aperture in the current fixed state, fuel injection volume TiO that is calculated according to new air volume Q is secured at fuel injection volume TiL or greater in order to achieve the engine torque for when fail-safe control is executed, and when air-fuel ratio.lamda.is less than the lower limit value.lamda.L, causing an increase in the amount of smoke, control is executed to suppress the occurrence of said smoke.