B4000 2WD V6-4.0L OHV (1994)
Idle Speed: Description and Operation
Intake Air Temperature Control System
PURPOSE
To provide thermostatically controlled intake air for improved engine driveability and reduced exhaust emissions especially during cold engine
operation.
OPERATION
The system uses manifold vacuum to manipulate air doors which control the intake air source I.E.. (fresh air or heated air).
Vacuum Flows Through Sensor When Cold
A Bimetal Sensor in the air cleaner housing regulates vacuum flow to the Vacuum Diaphragm.
Intake Air Flow Modes
The Vacuum Diaphragm controls the position of the Fresh Air Duct Valve.
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Fresh air mode vacuum IS NOT applied to the diaphragm
-
Heated air mode Vacuum IS applied to the diaphragm
The system will remain in the fresh air mode unless the Bimetal Sensor detects intake air temperatures below 24° C (75° F)
