90CS cruise control can't hold on

[Adam Recktenwald <audi@lucideas.com>]

Hello all,
I took my Audi out for a Interstate spin not long ago for the first time in
a month or two.  When I got to cruising speed and set the cruise control,
it held the speed for about 3 seconds then slowly decelerated (about 1-2
MPH per second).  It seems like it's trying to hold the throttle, but
can't.  I tried a few times to see if I was imaging things and each time it
was consistent.  I'm going of vacation on the end of the week and would
really like to have it.  Anyone else has had this problem or ideas on how
to fix it?  Much appreciate it.

-Adam Recktenwald
1993 90CS