> So, I'm left wondering if the ISV effects cold start. I think that it must
> as its function is to add air to the mix at the throttle, yes? So, if it
> isn't functioning and it is not adding air at cold start, then opening the
> throttle slightly at cold start is allowing the needed air into the
> throttle. Does that makes sense?
>
>
Yes, spot on. The idle controller watches the throttle switch and adjusts
throttle bypass air to keep RPM within a certain range. Standard tuning
procedure is to disconnect the idle stabilizer and set the bypass air on the
throttle body so the engine idles in the normal 850-ish range when warm, so
a warm engine theoretically doesn't really even need the idle stabilizer.
Cold engine, though, can definitely have trouble without it.

I suspect that the ISCU is kaput. Is there no way to test the ISCU itself? I
> haven't any method described in any of the manuals. It's an expensive part
> to swap in on a hunch.
>

If the ISV isn't "humming" with the key at ON and the engine not running,
something in the idle control system isn't working. The valve is controlled
via pulse width modulation, so when it's doing its job, it'll be vibrating.
It's unfortunately not all that uncommon for the controller to crap out.
Still, I'd check all the wires first, make sure the controller is getting
12v, it knows the throttle position switch is closing, and its connection to
the valve is OK before buying another controller.

--
John Bange