D50 4WD L4-156 2556cc 2.6L VIN 7 2-bbl (1982)
Fig. 21 - Dash Pot Adjustment
The deceleration system used on 1980-82 models includes a coasting air valve system, Fig. 18, and an air switching valve system, Fig. 19. The
1981-82 models also incorporate a deceleration spark advance system, Fig. 20, and on manual transmission models, a dash pot, Fig. 21.
The coasting air valve system and air switching valve system are used to reduce HC emissions during deceleration. The engine speed sensor which
controls the solenoid valve, will prevent the coasting air valve or air switching valve from operating at or below a specified engine RPM, by
opening the solenoid valve. On 1,400, 1,600 and 2,000cc engines, the specified engine speed is 1800 RPM (± 200 RPM). On 2,600cc engines, the
specified engine speed is 1600 RPM (± 200 RPM). This is done to prevent poor idling or engine stalling at lower engine speeds. The coasting air
valve supplies additional air to the intake manifold at engine speeds within the specified range, from a port located below the secondary throttle
valve. The air switching valve supplies additional air to the intake manifold at engine speeds within the specified range, from the idle mixture
adjusting screw passage located below the primary throttle valve. The coasting air valve and air switching valve are built into the carburetor.
On 1981-82 models the deceleration spark advance system, consists of an engine speed sensor and a solenoid valve, Fig. 20. During deceleration,
ignition timing is advanced by intake manifold vacuum acting upon the distributor vacuum advance unit diaphragm, which is routed through the
solenoid valve. At or below a specified engine RPM, the engine speed sensor will activate the solenoid valve, changing vacuum acting upon the
distributor vacuum advance unit diaphragm from intake manifold vacuum to carburetor ported vacuum.
On 1981-82 models with manual transmission, a dash pot is used to delay throttle valve closure during deceleration to its normal idle speed
position to reduce HC emissions.
