Not so fast. The idle valve behavior depends on the version of the FI
wiring harness. Lots of later vans power it from the fuel pump relay and
so on those vans it WON'T hum with just the key on, the engine needs to
be running for it to continuously hum.

Years 86/87 power it from the ECU relay and on those vans it should hum
whenever the key is on, engine running or not.

Mark

John Bange wrote:
>.............
>
> 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
>