Dashpot System: Description

To help control exhaust emissions during deceleration, throttle plate is held slightly open by means of a vacuum operated diaphragm (dash-pot). At speeds over 1650-1850 RPM (1820-2020 RPM on 3.0L engine), a speed sensor actuates a vacuum solenoid valve to vent diaphragm to atmosphere. A spring in vacuum diaphragm causes carburetor linkage to open slightly. As engine speed drops below 1550-1750 RPM (1700-1800 RPM on 3.0L engine), speed sensor interrupts current to vacuum solenoid valve, allowing intake manifold vacuum to retard plunger of vacuum diaphragm and return throttle to idle position.