This is used on 1975, 1977 and later models.
Closing of the throttle valve on deceleration is delayed in order to burn the air/fuel mixture more thoroughly. A vacuum controlled dashpot, attached to the carburetor linkage is used.
A servo valve detects intake manifold vacuum and closes if vacuum exceeds a preset valve. Since the air in the dashpot diaphragm chamber cannot escape, the throttle linkage opening is temporarily retained. If the vacuum is below the preset value, the servo valve opens and the dashpot works normally.
Inspect the hoses for breaks and damage, and the valve body for cracks.
- Have the engine running, brakes locked, and a tachometer attached.
- Push the dashpot rod, connected to the carburetor arm, upward and into the dashpot until it stops.
- Note the rpm at the dashpot stop and adjust to the following specifications. Note the time required between suddenly releasing the dashpot rod and the return to normal curb idle.
- The specifications are as follows: