The shutter is the problem. Some wear at the fulcrum, and move and stick in the open position. Runs better in cold weather right. Cold metal leaves more space to move back into place. Mine shifted up by almost 1/16th of an inch. I work at autozone and tried changing every sensor it had. Nothing worked. Changed the throttle body no more issue. $600 New through toyota. Used as low as $50 might have same issue. I paid $130 on eBay. No shipping. Came in 3 days.

 

Mine has settled in to idling right around 900, which is going to be good enough for me. Cold or hot doesn't matter.

 

Yeah, mine did the same. It came back after a few months. Lucas fuel sytem cleaner is only $4.99. It works for 6 months, in my 97 4runner at least. Hope it helps.