I had somewhat similar symptoms on my '84 1.9L: weak, rough.  But not
stally.  After checking my 02 sensor, plugs, plugwires, and grounding
connections (clean to brightness!) the solution wound up being the
replacement of a bad fuel injector.  This all started after a very
suspect tank of gas in a small town in Wyoming.

from personal experience rather than any real knowledge base i thus
suggest checking/cleaning the injection system...   [even comparable
between 1.9's and 2.1's?]

On Sun, 9 Jan 2005 21:18:33 +0000, Stew <stew@switch99.f2s.com> wrote:
> Earlier this year I bought a 78,000 mile 2.1L 1991 VW Caravelle.
> Took it for a good test drive - about 10 miles everything seemed fine.
> Ran it for a couple of months with no problems whatsoever and really
> began getting 'into it!'
> Decided to take a bit of a holiday round Europe (I live in UK), so
> managed to get a week off at very short notice and 'did Europe' -
> 1350miles in 6 days (couldn't get any more time off right then). It ran
> beautifully.
> Continued to use it as my everyday vehicle and for weekends away with no
> problems for a couple of months.
> I then took a trip to London (350 miles). Just before leaving I changed
> the oil, checked the plugs etc. ( I put them back in as the looked fine )
> Half way there, it seemed very low on power (It's the DJ engine -
> 112BHP). On getting off the motorway it kept stalling and generally
> running rough.
> Started to search the net - the first thing I found was about Oil
> viscosity - too thin and the hydraulic tappets don't lift enough - I had
> just used a premium brand multigrade and so I flushed the old oil and
> replaced it with the specified grade. No difference.
> The thing is - the ammount of power available varies from day to day -
> sometimes running a little rough other times really bad.
> It starts perfectly hot or cold.
> When it is cold, it runs fine - not sure about power - seems OK but then
> I never stress a cold engine.
> As soon as it warms up it will start playin up - if you pull up at the
> lights it'll idle for a minute or so, then stall. Starts fine again
> though and just needs to be kept at about 1100rpm to keep running. I can
> see no water in the oil, no oil in the water, and it seems to use very
> little of either. I have seen no evidence of water or oil leaks. (so I'm
> praying it's not pitted heads).
> I've searched through every vanagon page I can find and can see no
> symptoms that match what I'm seeing.
> I had a bit of a breakthough though - ever since getting the van, if you
> fill the fuel tank to the top it leaks (it was replaced by a garage
> about 6 months before i got it - I have the receipt) and I have read
> that the fuel filter blocks frequently. Took the filter off and emptied
> about 50cc of grey sludge out. Put it back on and it seemed to run
> better, so Iwent and bought a replacement - it ran a little better
> again. However - it then slowly deteriorated again. Tried emptying the
> new filter but it's clean, so tried it with the filter bypassed with a
> piece of tube - no different.
> I did have to change the starter motor a week or so before it played up,
> but as it ran fine afterwards, and I've checked to make sure othing has
> been dislodged.
> Anyone any ideas?
> Stew
>