I was just under it today and the tensioner is definitely not going bad. The belt isn't "too tight" or "too loose" it's about right. None of the pulleys really have much play in them. I may start by changing the idler pulley tomorrow becauze you that pulley has the "most play" when trying to move them.

 

they won't always have play when bad. they can feel right but still have bad bearings.

 

The sound is clearly worse when it's colder outside so I am really thinking it's a bearing in the idler pulley

 

good luck! noises drive me nuts.

 

Yeah.. they are the worst..

 

Replaced both pulleys on the auto tensioner a couple months apart on my a year ago. Or you can go the easy route and replace the whole thing. The bearing that feels rough or most noisy is usually the culprit. Good luck.