See Figure 1
This system is used on the 4A-F engines only.
The Hot Idle Compensation (HIC) system allows additional air to enter the intake manifold, maintaining a proper air/fuel mixture during idle at high temperatures. It also controls the vacuum supplied to the HAI valve, allowing heated air to enter the air cleaner during cold operation.
See Figure 2
- Check that air flows from the HAI diaphragm side to the carburetor side while closing the atmospheric port.
- Check that air does not flow from the carburetor side to the HAI diaphragm side with the atmospheric port open.
- Check that air does NOT flow from the HAI diaphragm side to the atmosphere port while closing the carburetor side below this temperature 72°F (22°C). Using a hotwater bath, heat the HIC valve to above 84°F (29°C).
Do not allow water to get inside the valve.
- Check that air flows from the HAI diaphragm side to the atmospheric port while closing the carburetor side.