Non Fuel Injected Models
When engine coolant temperature rises above 129°F (54°C), a bi-metallic vacuum switching valve (BVSV) opens purge line between canister and throttle purge port. As engine speed increases to a moderate level, throttle valve opens purge port to manifold vacuum and canister vapors flow through purge line and into combustion chambers for burning.
As engine speed drops to idle, the throttle valve closes off purge port to manifold vacuum and canister purging stops.