I need to change my idler pulley, its not putting any tension on the belt. Can someone tell me how to change it?

I need to change mine because it's making a loud noise. However, in your case, you said it's not putting any tension on the belt. That sounds like the long bolt that threads through the pulley may have slipped down and lodged itself into a crevice which is why you can't get tension. It happened to me once, which is why I am assuming you have the same problem.

Try putting a screw driver from underneath the rear of the pulley bracket and push the long bolt up this should get the pulley working again.

I am going to change the whole thing as I have 102k on my car.