Dodge Intrepid

I have dodge intrepid 2000, with 2.7L engine and 82 000 miles on it, have that kind of problem. Engine sometimes shuts off while I drive and slow down, or engine shuts off when engine is on Idle and as I cranck it again it starts without any problem, but sometimes it will not start immediatly, I changed engine control module but did't help. I have no check lights on and diagnostic is not showing any malfunction. At the shop they can not diagnoze whats wrong with car. Today I was tapping on throtle positioning sensor and RPM was going up to 1200 then I disconected plug and RPM went down to 700, after a while engine shuted off, then I conected and engine run normal, disconected again and rpm go up to 1200. Shaking plag on sensor was making rpm go up or down. What can be wrong?