Exhaust Emissions System - Exhaust Gas RECIRCULATION: Description
On 1975-77 models, the Exhaust Gas Recirculation (EGR) system consists of an EGR valve, a Ported Vacuum Switch (PVS), exhaust gas crosspipe, vacuum amplifier, vacuum reservoir, and various connecting lines. See Fig 1.
On 1978-79 models, the EGR system is a two-port system, being vacuum-controlled by two connections on the throttle valve housing. System operates to control formation of NOx emissions. This is accomplished through recycling exhaust gas from the exhaust manifold back into the combustion chamber. System consists of an EGR valve, ported vacuum switch, vacuum holding valve, vacuum release valve, EGR crosspipe, and vacuum tubing.