cruise control surging?

[03wr250f]

Alright so I was coming home from a weekend trip, I had been using my cruise control off and on when certain annoying cars were going 5-20 mph below posted. Apparently rain scared them, but i guess better for them to go slow, so whatever. My cruise control has always worked well except because of an autozone throttle cable it will pop off the ball and socket if you punch the throttle many times when it is set. A simple popping it back on the ball and you are good as new. That had been my only problem with it ever until tonight. I had shut my cruise off to pass a car because before hand I had to slow down until a appropriate passing opportunity. I got around the car and went to turn cruise on again. I noticed i had a heck of a surge. It would set just fine, but then it would lose speed 5 mph and then throttle hard to get back to speed or even over set speed 1-2 mph. I tried it several different times I even shut the truck off and restarted it, tried different speeds, nothing. Brakes still work fine as does heater/ac so I dont think I lost vacuum. I also tried several different speeds to see if it was a certain speed, no luck. Speedo doesn't bounce, I am wondering if because of lots of rain something may have died? But that is the thing is my underhood is always dry. This was no different. Could my steering wheel switches have died? Any thoughts?
I searched google and didnt find much for a diesel doing it that wasnt a PSD. I also used the search here and didnt find much.

 

[SLC97SR5]

Mine has always surged right @ 50mph. I've cleaned connections and wiped off the rear axle speed sensor. No fix. I simply avoid 50mph.

My guess is the rain crept in somewhere it shouldn't be.

 

[03wr250f]

i am wondering if that might be the case or possibly even the vacuum line on the brake pedal got cocked at a weird angle and allowed a leak, because there is a bit of play i the bushing for the valve there. It worked pwerfectly fine yesterday. I made a 600 mile trip and simply shut the cruise off when needed and reset it after. No problems. So I may just run it.

 

[jayro88]

Mine does this from time to time. Mostly when it is raining really hard. I know that a sticking cable can cause it. Many time just lubricating the cable will fix it.

With mine, if I turn the vehicle off and then restart it it will usually begin working correctly again.

 

[franklin2]

It could be the vacuum dump valve is set too sensitive on the brake pedal. So it dumps the vacuum but does not activate the electrical switch on the pedal. I would check it, and move the vacuum switch away from the pedal arm a little bit.