Cruise control wasnt working and I just plugged.

Cruise control wasnt working and I just plugged it in and it worked. One week later the idle is going from 1200 to 2600rpms. It just reves up to 2600 and immediately back down to 1200. And this just keeps looping over and over. Each loop takes about 5-8 seconds. I have unplugged the cruise control and the loop still goes on. The idle problem occurs in all gears, From a dead stop the car will idle up to 40 mph without me touching the gas.