Hi team,

I have a question regarding the Idle Air Control Valve on a 3VZ-FE engine.

The IAC Valve has two air hoses attached. An upper hose, and a lower hose.

The upper hose is obvious, it receives filtered from the air cleaner box, and that gets metered by the IAC Valve into the intake plenum.

But there's a second air hose underneath the IAC Valve, which appears to join the block somewhere in the middle of the vee.

I'm curious. What is the role of the 2nd lower air hose?

Thanking you all in advance.


The tube facing horizontally to the left of picture is the "lower air hose" connection

 

Hello,

It is a weird IAC valve, it has at least one more port than I expected.. The big inlet is for the air from the filter, the mounting surface has a valve itself, which would be an outlet. Two out of four regular ports should be for coolant to prevent the valve from freezing. One of two remaining is for a Power Steering Idle-Up function, so that when the load on the PS system increases, the idle would go up to prevent stalling. Last hose is a supplementary, or Air Assist line, which is connected to the manifold and uses vacuum in the manifold for a more precise idle control, at least I think that's what its function is.

That's what I managed to gather, and since I don't own a car with this valve, I can't be certain of all the functions, the only way to find out for sure would be to take it all apart and inspect where all the hoses are going.

Hope this helps and best of luck!

 

Thank you for responding.

Upon further research, I was able to ascertain the lower hose in question connects to an air tube gallery on either side of the intake manifold.

It's officially called Toyota's "Fuel Injector Air Assist" function, and it only operates when the IAC valve is closed.

The "Fuel Injector Air Assist" function allows a fine jet of air to rush by each injector tip, improving the atomisation of the fuel injection stream.

So there you go!

 

Huh, that is actually quite interesting, thanks for sharing this! I wonder why they did away with that system as quickly though, it was only really present in mid-90's, never to appear again.. Maybe an improved injector design made it possible to go about it without air jets..?