Jeff, I had a problem with erratic idle on my 88 GL, as you describe.
With the engine warm, I disconnected the idle stabilizer valve and the
erratic idle stabilized. Supposedly the idle stabilizer is cut out of
the circuit when the engine warms up, but if there is a fault in the
idle stabilizer circuit - either the ISV(up on top of the engine or the
Idle Stabilizer Control (ISC) - a black box located just forward of the
right hand brake light (remove the tail light for access)- this erratic
idle can occur.

If this is the source of the problem, you can drive quite safely with it
disconnected until you can get the right repair.

The idle stabilizer circuit does three things.
1) Kicks up the idle until warm-up after a cold start
2) Kicks up the engine RPM to avoid stalling when the power steering
turn limits are reached ant the power steering pump is loaded.
3) Kicks up the RPM to avoid stalling at stoplights, etc, in traffic,
when the air conditioner cycles on and off.

Good Luck.

John Rodgers
88 GL Driver
Jeff Hartman wrote:

> Hi, I have been struggling with an unstable idle. It is very cyclic
> and the
> cycles and frequency increase with an electric load (fans etc.) With
> the O2
> sensor and temp sensor replaced, and other tuneup adjustments made,
> the VW
> dealership claims I need a mass airflow sensor. This was determined
> without
> any computer diagnostics. In fact the dealer's service department says
> that
> their new computer testing equipment no longer can test our obsolete
> Vanagons.
>
> I don't have a lot of faith in them, so do you have any ideas of whether
> they are right and what I should test next? I made a cursory review of
> the
> archives over a couple of recent years, without finding this exact
> problem
> described.
> Thanks, Jeff Hartman
> Juneau, Alaska
> 86 2.1 Vanagon
>
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