PURPOSE: To perform an accurate air fuel ratio control by intermittently feeding back mechanical displacement of a fuel measure in the electric phase to an electronic controller and correcting an air fuel ratio by means of a pulse motor.

CONSTITUTION: A signal of a suction air amount is sent by a displacement detector 12 of an air valve 2 to an electronic controller 13, which generates a driving current. A pulse motor 11 operates on the current to control a measuring needle 16 of a fuel measure 7. A mechanical displacement of the pulse motor 11 or the fuel measure 7 is converted by a displacement detector 12 in the electric phase, which is intermittently fed back to the electronic controller 13. When an air fuel ratio is unequal to a specific value, the pulse motor 11 corrects it. An air fuel ratio can be accurately controlled.