2001 Dodge Dakota idles up and down when you push the clutc

When im coming to a stop or go to push the clutch in the rpms jump from 600 idle to 1,000 and back down till I stop. I have a underdrive pulley on it so sometimes it drops lower but the company even says it will do that cuz its turning so slow. I cleaned the tps sensor and checked my other sensor to see if that was the issue just fixes it for a couple miles