Hi Chad

It could be both, it is hard to say. Many mechanic guies change both units.
They are expensive devices. This is why I am trying to fix it.

The ISV should read continuity on a multimeter.

I am still experimenting on those devices. Here is what I have done so far.
My idle valve (ISV) seems to work OK when I put 12 VDC on it. No power,  the
valve is thight closed, with power, the valve open (No humming because the
ISCU is the solid state unit which can modulate the valve). After changing
some composants in the ISCU, I put 12 Vdc on it with the ISV connected to it
and the ISV was humming. After that I put back all the devices on my engine,
and I turned on the ignition key (without starting the motor)  I could  feel
the ISV humming with my hand. After 10 or 15 seconds, the ISV stopped
humming. I decided to start the engine and it started very fine, better than
when the ISV was disconnected but after a while the engine started to surge.
When i disconnected the ISV, the engine was idling fine.

I have checked the gas throttle switch and it seems to be OK. Next step, I
am going to clean the ISV with a brake cleaner.

Germain

----- Original Message -----
From: "Chad Morris" <chad@ALLMORRIS.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, September 10, 2003 7:08 PM
Subject: idle stabilizer: valve, control unit or both?

I am experiencing the ever so common high idle problem on my '89 Carat.
Don't hear the infamous hum or buzzing sound coming from the idle stabilizer
control valve (how loud is that supposed to be, anyway?), but if I
disconnect the wiring harness going to the valve while the engine is
running, the idle immediately settles right down to 850 RPM.  If I put the
plug back in, the idle speed stays at 850 RPM, no change.  Does this
indicate a bad valve, control unit, or both?

Aside from replacing with "known good parts", of which I have none at my
disposal, are there tests I can perform with a multimeter to determine
functionality?  Can I apply current directly to the valve with the engine
off to see if I hear the buzzing?

Chad Morris
'89 Carat
Salt Lake City