Century V6-260 4.3L DSL (1984)
Thermal Vacuum Valve: Description and Operation
EGR Mixture Temperature Control (EGR-MTC)
On models with this system, EGR valve operating vacuum is controlled by a temperature sensitive vacuum switch mounted in the intake manifold. The
valve senses intake mixture temperatures and blocks the EGR valve vacuum signal when temperatures are below 70° F. The valve is a two port type with
the bottom port connected to the vacuum source and the top port connected to the EGR valve.