Cruise Control erratic '99 Prerunner

The cruise will continuously accelerate then decelerate after you set it. The rate of change isn't large but it is just like someone that pumps the gas while driving because they can't seem to hold a steady speed - yes, my wife once did this
The full range of speed is probably around 5 mph.
I hate to have the dealer charge me $100 to say "this vacuum hose was leaking" plus have my taco at the shop all day.
Anyone have a similar issue and a solution?

 

My 02 has always worked like crap, same for my 96. I just don't use it unles I'm hauling ass at 80+, then it works fine.

 

Same issue here...though inconsistent. Is it an aftermarket control?

 

Both stock, when it hits a slight hill it surges the gas and up's the rpm, then it abruptely backs off again when back on the flat. I wonder since I lifted both trucks and put larger tires on if this didn't help cause it to be less effective.

 

That actually sounds normal? Mine does that on hills because it's trying to maintain the speed its set at and the hill presents a problem with maintaining that--it'll brake going down hills too in order to stay at the preset speed. Although if its over-doing the rpms that could be a problem. I find cruise control a bit freaky in general. But then I'm a control freak...

 

I just don't use it anymore, after riding my wife's acura which handles perfectly with the cruise control I can't stand the flucuation with mine.