For about six months my cruise control would not stay at any set speed. It would just continue to creep up in speed. Tried cycling it on and off numerous times with no luck. About 2 months ago I disassembled the TPS and cleaned it completely then relubed the insides with dielectric grease and the bushiongs with lithium grease. Since then the cruise has worked sweetly and the transmission no longer jumps in and out of lock up. Some where in the software of the computer I suspect the TPS feeds info for the cruise control. Figured I would share what worked for me. My next step was to buy a new cruise servo. I had already checked all the vacuum lines.