Type 85 cruise control

[Jason Mawhinney]

Anybody else out there have their cruise controls not work properly at ~40
degrees and below?  You can set the cruise and feel the pedal "lighten"
under your foot but doesn't seem to have enough strength to hold the
speed.  Its really strange since the cruise controls on both my cars work
exceptionally well in warm weather.  I would think that someone else out
there has this problem since both my coupe and my 4kq 20v have this problem.
Anyone have any ideas on what to check?
Jason
'85 4kq 20v
'86 coupe GT
'87 5ktq