All Models Except Federal Civic Hatchback with 1500 Eng. & Man. Trans.

The throttle opener is controlled by a solenoid valve, control valve, and speed sensor. When vehicle speed is above 15 MPH, the speed sensor causes the solenoid valve to open and allow manifold vacuum to the control valve.

Fig 1: Throttle Control System Diagram (All Models Except Federal Civic Hatchback with 1500cc Eng. & Man. Trans.)

Courtesy of AMERICAN HONDA MOTOR CO., INC.

When the manifold vacuum exceeds a preset value (which occurs during deceleration), the valve opens and the throttle opener opens the throttle a small amount to improve combustion.

When vehicle speed drops below 10 MPH, the speed sensor closes the solenoid valve, control vacuum drops, and the throttle positioner vacuum is relieved through an orifice. Carburetor return spring tension closes the throttle.

Fig 2: Throttle Control Valve

Courtesy of AMERICAN HONDA MOTOR CO., INC.