1979 Accord & Prelude

The throttle control valve used on these models incorporates a dashpot check valve. This check valve is separated from the control valve by a second check valve. Closing time of the throttle is regulated by both the dashpot check valve and the atmospheric pressure sensing bellows, which controls tension on the diaphragm. As altitude increases, less vacuum is required to keep the valve open, thus keeping the throttle open longer.