Question about heat rise valve in manifold?

[chengny]

That's an EFE (early fuel evaporation ) valve. Here is the diagnostic chart.



The way I read it (the right hand side of the chart);

When coolant is cold, the TVS is open. This allows manifold vacuum to act on the diaphram of the EFE valve actuator, which causes the butterfly to close. When operating temp is reached the TVS closes off manifold vacuum and opens to atmoshere. Loss of vacuum allows the EFE valve to fully open.