Greg, Actually the Bentley Manual (big green one) has an awesome step by
step troubleshooting diagram for the for the cruise control.  Just
follow it and you will find the problem.

Hope this helps,

Ken Wilford
John 3:16
www.vanagain.com

PS I also have a Bertone X1/9!

Gregory Smith wrote:
> Hi Gang,
>
> My '88 has a factory installed cruise control system which is having
> difficulty maintaining speed.  It works at first and then it's ability
> falls off quickly, in less than a minute, as if it is losing vacuum.  I
> have check the vacuum lines that I can see connecting to the system,
> but I'm not 100% sure I know what all in included.
>
> Can anyone point me to an online diagram that covers the system?  In
> particular in the rear.  For instance I don't know what the device in
> the right rear corner (just to the left of the taillight) with vacuum
> lines and a wire harness going to it is.  It has a vacuum line going to
> it (connects to the throttle servo), but there is an unused nipple just
> below the one that has the line on it, perhaps it needs to connect to
> something?
>
> ANY tips are appreciated.
>
> Ciao,
> Gregory Smith
> Olympia, WA
> '87 Bertone X1/9 Corsa
> '88 VW Vanagon
>