Date:         Mon, 21 Apr 2003 20:50:50 -0500
Reply-To:     Joel Walker <jwalker17@EARTHLINK.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Joel Walker <jwalker17@EARTHLINK.NET>
Subject:      Re: Getting a handle on Idle problems..
Content-Type: text/plain; charset="iso-8859-1"

> <<<the idle stabilization valve
> <<<- is not a 'fan' ... it's a solenoid that pushes open/close
a
> <<<small valve.
>
> Inside mine, it is a fan that spins, cleaned it off with carb
cleaner and it
> spun as I sprayed it...

what you have on your bus i can't say .. what is on my four buses
isn't a fan. going by the vw documentation, which doesn't call it
a fan but a valve, and the fact that when hooked up without the
hoses, no air can be felt flowing through it.

>> <<<- the air permitted to pass through the valve is NOT
metered.
> look at the hose connection ... the hose from the valve
connects
> between the throttle body and the air flow meter:
> downstream/after the metering of input air....>>>
>
> The air going through the valve IS metered/measured by the AFM.
It is AFTER
> the AFM and any change in volume is detected by the AFM

on that one, you're right .. i'm looking at the wrong hose. the
idle stabilizer valve opens and closes a bypass around the
throttle plate .. not from the crankcase ventilation, as i said.
my error. :(
hmmm. wonder if i hooked those back up in the right place??
shouldn't really matter, i guess.  anyway, the valve allows
METERED air (as bob says), but the crankcase vent hose is the air
that is unmetered.

>An increase/decrease in air flow by the valve is detected by the
air flow
>meter flap moving changing resistance and therefore changing
amount of
>DETECTED air flowing through the meter

that part i'm not so sure i agree with .. probably a difference
in terminology, though. it seems to me that since the air has
already passed through the air flow meter, it's been metered
once. anything that happens to it after the meter is not detected
by the meter .. if it were, then a vacuum leak (say a split in
the rubber elbow between the air flow meter and the throttle
body) would be detected and you wouldn't have the problems we do
with such leaks. all the valve does is let air bypass the
throttle plate when it's closed (like at idle). the air that is
doing the bypassing has already made it past the air flow meter.
and all this is orchestrated by the idle stabilization control
unit, which is monitoring all those sensors that go bad. :(  but
it does work a lot better than the old carburettors ... with all
their dashpots and seasonal adjustments of the choke.

joel