Hey, like I said in my previous post... just got back from a long trip.
Had some 'issues' with my cruise control.

Noticed that when you pushed the "Accel/Set" it often would not "set" and would never "accel"... unless you were going downhill.

Also, sometimes when it did "set", say at 110kph... it would slowly dip down to ~85kph over a period of 20seconds, and then take about 30seconds to climb back to ~105kph.

I also found that it was easier to "set" the cruise control when she was in "Drive" rather then "Over Drive".

Hills were bad too..... she wouldn't rev up to keep her speed up, and she would just crawl up the hills.
It seems that cruise control was more like RPM control, and it didn't change.

(I'm sure there are tons of posts on cruise control... but it'* 2am and I'll search tomorrow)
If anyone has any ideas or knows a post that is a good read... please feel free to post.

i got no help for you, just letting you know that our old 88 grand voyager did the same thing...annoying as hell, but we worked around it.

somewhere around this mess, I have instructions printed from http://www.batauto.com about rebuilding the cruise servo. I have never tried it but it looks really simple. Our 90 does the same thing. I have given up trying to use it until I get a chance to dig into it.

Yea if you find it... be sure to post it... I'd love to try.