DESCRIPTION
The hot air intake (HAI) system adds hot air supply to carburetor in cold weather to improve driveability and to prevent carburetor icing. Carbureted Corolla and all Land Cruiser and Tercel models use a hot idle compensation valve (HIC) to control opening and closing of air inlet door. Pickup and 4-Runner models use a separate thermal vacuum valve to operate heated air door.
OPERATION
When intake air temperature is low, vacuum valve is closed. Intake manifold vacuum will act on heated air door diaphragm. This causes diaphragm to pull up and close cool air intake. As intake air temperature rises, thermal valve opens, allowing cool air intake door to drop and allow unheated air into air cleaner.
HIC Valve-Type Hot Air Intake System Thermal valve type used on Pickup and 4-Runner is similar. Scheme 16
AUTOMATIC HOT AIR INTAKE
- Visually inspect all hoses for proper condition and connections.
- With engine idling, check that cold air intake is closed when engine is cold and open above specified temperature.
- If system does not respond properly at given temperatures, check air door or linkage for binding, and replace thermal valve as necessary.
| Application | Closing Temp. °F (°C) | Opening Temp. °F (°C) |
|---|---|---|
| Land Cruiser | 81 (27) | 91 (33) |
| Pickup & 4-Runner | 86 (30) | 113 (45) |
| All Others | 72 (22) | 84 (29) |
HOT AIR INTAKE SYSTEM OPERATING TEMPERATURES