Germain, Chad,

there are probably many causes for this idel instability. Here two of my
recent encounters:

a) Engine races after startup, then cuts off - would not have enough power
to drive:
Long trouble shooting & frustration, finally turned out to be connectors on
the idle control unit which had broken solder joints on the board: a couple
of the large metal spades cracked the solder and had intermittant/no
contact (a failure we see frequently in heat cycled electronics): re-solder
and all was fine

b) Oscillating RPM (600...1200)
A combination of poor contact to the ECU (the connections were corroded)
and a worn air mass sensor (change spring tension by one notch)

Just some hints, solder or change AMS parameters at own risk... :)

         Wolfgang

At 08:37 PM 9/10/03, Germain wrote:
>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