It's to supposed to do that, no matter how rainy or wet it is.
Something is not working like it should.
spark plug wires pop into my mind.

'stutters' ...........does that mean runs roughly or poorly during
acceleration ?
what does that mean exactly ?
is it low on power when it does it, like it's only on 3 cylinders ?

describe the symptom more please.

----- Original Message -----
From: "Matthew Snook" <matt@SNOOKSBAND.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, January 07, 2009 12:00 PM
Subject: stuttering

I have been driving around ('84 Waterboxer 1.9) in the soaking-wet
conditions here in the Willamette Valley in Oregon, and have noticed that on
wet mornings the engine stutters at low rpm until it is completely warm.
This never happened at home, where it's dry - even when the temperature got
down around 10 degrees Fahrenheit.  So I don't think it's the cold, it's
the wet weather.  Is this a typical symptom in wet weather, or is it time
for a more general checkup?

Matt