Cruise control surgings

[afinney@tamsconsultants.com]

Well, I took a long hard look at the cruise control system this
weekend. My first observation is that the first test Bentley
specifies for the early style cruise control is misleading. The
test lamp should not light. After much quality diagnosis time
with a hand vacuum pump I determine that the previous
owner connected the vacuum lines at the vacuum pump to
the outlet side. I was blowing air into the system. With the
hoses reconnected and after a thorough vacuum check the
cruise control came to life. Now it surges. Remembering the
post on surging I cleaned and regreased the speedo cables. I
also took apart the black box oxygen sensor counter thingey
and cleaned in there. This is a must do operation for anyone
with a bouncey speedometer. Now the speedo is rock solid
but the cruise still surges. It would be using more fuel than
without it. The boost gauge cycles from good vacuum to
atmospheric. Where elso do I look. I've got two good cruise
brains. Neither change the situation. The only thing I can
think of that would do this is the computer controlled vent
valve in the vacuum pump for the cruise control. Does anyone
have any idea what's going on here?

Thanks, Andrew Finney
1983 UrQ. (under the cosmetic knife for the next month)