Vanagon F4-1915cc 1.9L (Water Cooled) (1983)
Deceleration Valve: Description and Operation
The purpose of the decel valve is to control the amount of unburned hydrocarbons entering the atmosphere from the engine during deceleration. This is
accomplished by the decel valve opening on deceleration, bypassing the closed throttle plates and allowing fresh air to enter the cylinders. This results in
a leaner fuel mixture, thus reduced CO and HC emissions.