OT: Jetta idle

[greg.rocco at gmail.com (Greg Pallett)]

A funny thing has been happening with my Jetta lately.  When the rpm's
drop from to idle, they drop pretty low - to maybe 500 or so.  The car
shudders and you think it's gonna stall, but then it corrects and goes
back to idle at 900ish.  It happens when the car is warm, when I come
to a stop.  It dosen't happen when shifting, there's not enough time
for the rpms to drop to idle.  Sometimes sitting at long red lights it
will just go from it's 900ish idle, stumble to 500, and then pick back
up.
Any idea where to start troubleshooting this?  I'm tempted to blame
the ISV, that seems to be a common culprit in mk2 Jettas...
Thanks!
GP

-- 
"Fatal mistakes rarely happen, but funny things often do"