Nope. 
Not even slightly.
It's not connected to anything. It just picks up a signal from a bump on the
flywheel. 
I find 1.9's to be 'fiddly' about getting them to work exactly perfectly
when they get off.
I've spent hours playing with everything on them sometimes.
The two biggest things that stick out in my mind are idle switch contact at
the right time,
An temp sensor for the ECU and the connections to it, the sensor isn't weak
( darn, sorry to ruing someone's fun about running out to buy a new one )
...I rarely find an actual bad sensor ...but the connection to it, you can't
look at that too carefully.    < and I hope no one's spark plug wires are
15+ years old, same for coil, if it's ancient, it's suspect > . . Guess
that's more than two items - lol ! 
And perhaps oxygen sensor, and assuming air flow meter is good, tho I
wouldn't expect much affect at idle from an AFM that's not perfect. 
s. 

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Roger Sisler
Sent: Tuesday, November 27, 2007 4:25 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: what is this wire...?

My 1.9 has that , too. Do you suppose it could contribute to surging idle if
grounded or something?