Vacuum Diaphragm Unit

This unit operates on intake manifold vacuum. When vacuum is applied, unit pulls on clevis rod and through other linkages rotates throttle plate into a slightly open position. Amount of opening is controlled by travel of clevis rod which is limited by travel adjustment screw. As long as vacuum is applied to diaphragm unit, partial opening of throttle plate is maintained when accelerator pedal is released, and accelerated idle is obtained.