The deceleration control system on B2200 carburetor equipped Pickups is designed to maintain a balance air/fuel mixture during periods of engine deceleration. Although the components used vary in some years, the basic theory remains the same: To more thoroughly burn or dilute the initial rich mixture formed when throttle is suddenly closed, and to smooth out the transition to a lean mixture by enriching the mixture slightly after the throttle has closed. Although the process may seem contradictory, they act in sequence to provide an overall ideal mixture.
The deceleration control system used on carburetor equipped B2600 models and on the MPV reduces the fuel flow to decrease HC emissions and to improve fuel economy during deceleration and cut the fuel flow when the ignition switch is OFF to prevent "run-on''.