A conveyor chain has lower pins and is displaced in steps through a station. The storing unit is used for receiving the supply voltage to store energy and releasing energy to generate an standby voltage when the power supply stops providing the supply voltage. Once the contribution of each basic template to the overall imbalances is computed, templates of same magnitude of imbalances but of opposite direction are imposed to restore air-fuel ratio balance among cylinders. The controller also moves the actuator when the lever is not in the park position and the interlock switch is actuated.