I have an 83 Air cooled and I get some of the same symptoms. I get
800-1200 rpm periodically, I just live with it cause I can't see that it
hurts anything with a manual transmission. Might be more important if you
have an automatic.
I've read on the list to first check for vacuum leaks. Next check for
fuel leaks at the injectors, the hose may look good but they often have
very slight leaks that appear only when you wiggle them when they're
under pressure (I've found this situation).
The other thing is that you could be getting sporadic rich lean mixture
because your AFM has some minor resistance on the contractor plate (never
opened mine).
My 83 has deceleration valve and I suppose that you could add one of
these to your 81 but I can't say it would improve anything or fix your
problem.
Low fuel pressure is something else you should check.

Stan Wilder
83 Westfalia Air Cooled.

On Sun, 15 Jul 2001 17:47:42 -0400 puzerewski <puzerewski@MSN.COM>
writes:
> Volks,
> I got it to idle ant around 900 today, but when hot it wants to idle
> at
> around 1500.  This is an FI motor.
>
> Also, when cold, is not smooth right away.  Timing is set at 7.5
> BTDC at
> idle, and 42 degrees total.
>
> I notice the timing "jumps around" when around 42.............The
> mark does
> not stay more or less in the same spot, like there is a miss or
> something
> going on...........New cap, plugs and wires to no avail.  I am
> beginning to
> wonder if I don't have a crappy injector..............any thoughts
> here,
> anyone BTDT?
>
> Changed the oil, swapped the oil pressure spring with one from
> another case
> I had, and oil pressure seems to be up.  I have just driven it a few
> miles
> around town, so cannot really say too much.
>
> Any serious ideas would be appreciated.
>
> Adam Puzerewski
>
> 81 westy
> 74 beetle
> 73 Transporter (new!!!!!!!)
>
> Vanagon Partsmobiles

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