On the 3.0; the pulley next to the air conditioner is the tensioner pulley or the idler pulley?

 

That is the A/C tensioner pulley.

Sounds to me like you are talking about timing system components though

 

I am changing the timing belt, but while I'm at it, I want to change this pulley; which has been squealing. Some parts listings call it an idler pulley; others call it a tensioner.

 

im going to have to say tensioner pulley. mine locked up on me and i just cut the belt so i never used my ac again but thats me thou

 

That is the AC tensioner pulley. Be sure to match it up, because the only Idler pulley is in the timing system, so make sure they are not talking timing tensioner

 

considering the fact that you turn that bolt your socket's on to adjust the belt TENTION, I'm going to go with tentioner pulley

 

The parts I have seen listed as "Idler Pulley" are also tensioning pulleys; perhaps for vehicles that do not have an A/C compressor and the pulley in the photo. Here it is identified as an idler pulley.

 

Well, the guys at Rock Auto; who had both idler and tensioner pulleys listed, told me they are the same part. Not confusing or anything.
Also; my pulley turned out to be fine. The tension adjustment bolt fell out of the spindle. The belt was probably squealing as well as the pulley spindle that was probably spinning as well.