For first time since owned truck 4yrs ago this has happened. After work my drive home is 20mins and ac ran out of Freon so stopped at Walmart came out 15mins later and hit auto start on fob and was about 30ft away and could hear engine seem like idle was way higher than normal almost like a regin high. I got in and to make sure it was mine I was hearing I turned it off and then back on and same thing. So I backed out and drove home which is 2 blocks and got home idle normal then it went high again but rpm was still at like 600. Around the fan shroud it seems like I hear a noise that's hard to describe kinda a clicking but not. If I give quick rev the engine still sounds high RPM. My truck has only regin 2 or 3x since owned it and that was from it idling for few hrs while I slept in it. Any ideas are greatly appreciated