When you take off the idle speed control valve, there are three seperate compartments.
Two have air flowing between them, with the little valve in between which regulates the volume of air passing through.
The third one is a completely seperate compartment in the ISCV and throttle body that fills with coolant.
If when you connect the coolant lines up, it leaks coolant into the throttle body, then you must have some leaking or perished gaskets, which normally seperate these areas. This could also cause a poor idle when the lines are looped off, as you will effectively have a vaccum leak, air that hasnt been 'read' by the airflow meter will possibly be getting into the throttle body.
Also just looking at the Toyodiy website, I just realised that there's actually a thermostat in the throttle body for those coolant lines.
I guess it must only flow coolant through there when it is especially cold, rather than heating it up all of the time.
I was the one who had the ISCV hooked up for quad throttle setup, and I machined through to the third compartment, so that I could use the coolant pipe as the air feed.
