Blake, the idle stabilizer on my 88 GL gives me the same trouble, so I am
running with it disconnected. It runs real somooth that way. Without it,
however, cold starts are a pain, because the Idle Stabilizer Valve (ISV) keeps
the engine idling at 1000 rpm when cold. The operation of the valve is related
to the signal from the Temp II sensor to the ECU. Cold, the ECU circuit
signals the ISV to do its thing and regulate idle speed. Once warm the Temp II
signal is cut from the circuit. So if you disable the ISV the signal from the
ECU has no place to go, so the engine will stumble until it warms up. After
that, it runs smooth.

The other thing the ISV does is kick up the idle speed if the AC is turned on.
If you are slowing down or stopping for a light or something and the engine
idles down, the load from the AC will kill the engine unless the idle speed is
kicked up a bit to carry the AC compressor load. So the ISV does its thing.

I two would like to know why this problem with the ISV even exists. I have not
found a solution except maybe replacing the thing, and its an ex-ensive item
on the later vans.

John Rodgers
88 GL Driver

Blake Thornton wrote:

> In an effort to find my electrical gremlins, I bypassed the idle
> stabilizer.  My idle went from "searching" to smooth.  I wan't running
> poorly before (except when the gremlin took over and killed it), but with
> the idle stabilzier bypassed, it seems to be running much better.
>
> Could someone explain to me what the idle stabilizer does and what happens
> when it is bypassed.
>
> Thanks,
> Blake
> 84 Westy
> SLC UT