K 2500 3/4 Ton Pickup 4WD L6-292 4.8L VIN T 1-bbl (1982)
Idle Speed Control (Linkage): Description and Operation
Fig. 48 - Throttle Return Control (TRC) System Schematic
PURPOSE
Reduces hydrocarbon emissions during coasting--Fig 48.
OPERATION
During coasting the control valve allows vacuum to act on the throttle lever actuator holding the throttle valve slightly open to admit more air to
the combustion chambers--leaning out the overrich mixture caused by the sudden closure of the throttle plates.
When manifold vacuum drops below a predetermined value the control valve closes allowing the throttle actuator to return the throttle valve to
normal idle.
