Idle/Deceleration Vacuum Switch (Turbo)
The normally closed idle/deceleration vacuum switch is open whenever vacuum is applied from the carburetor spark port. See Fig 1.
Vacuum to switch is controlled by a ported vacuum switch that opens at a coolant temperature of 95°F. The idle/deceleration vacuum switch signals the ECU to switch from "Open Loop" mode to "Closed Loop" mode.