100% agreeThe manifold vacuum port is always allowed some flow. When the main atmospheric vacuum port (the one on top) is closed, this causes vacuum to be applied to the HAI motor.
I'll circle back to this...When the temperature actuator starts to open the valve, the main atmospheric port opens first. This causes the entire body of the valve to be opened to atmosphere.
Also 100% agreeAs air intake temperatures continue to climb, the valve will open more, allowing more atmospheric air to flow into the valve. Simultaneously the manifold vacuum orifice opens more, allowing more air into the manifold. The idea of this is, is it will lean out the idle and part-throttle cruising mixture.
This is the HIC circuit in a nutshell. Well thought out, well designed. I'm not an engine expert so I don't know how big of a difference it makes to idle and part-throttle driving. A little? A lot?This is because hot air is less dense, and needs less fuel to burn. At mid-high throttle, the air intake temperatures will naturally drop because of the increased air flow. High intake temperatures are really only an issue at idle and low throttle when their airflow is slow enough that it has time to pick up a significant amount of heat from the engine bay. But the whole body of the valve will be at atmospheric pressure unless the inlet port is restricted.
I am going to open up myIt's simple enough to check the operation of the mechanical part of the valve: Unscrew the temperature actuator and poke something into the valve and observe what happens. It's probably just a little stuck and needs to be lubricated.
The PCV nipple is never directly open to atmosphere. The bottom half of that valve is a variable orifice (restriction). That's why the diagram has that area shaded in black in all 4 operating modes - because it will always be in a deep vacuum.So, let's come back to your statement: the entire HIC body is open to atmosphere at hot conditions. That would include both the HAI nipple, the PCV nipple