My 86 Coupe DeVille has a loose pulley, i im not sure if its the tensioner pulley or the one on the other side of the alternater, because i can wiggle each of them a little bit when i take the belt off. I dont even know what the one to the left of the alternater does or what it is attached to. the worthless Haynes Repair manual doesnt even say what pulleys do what or anything even related to them. i sprayed WD40 on the nesioner pulley and the other one and the screeching stopped for about 5 seconds. i guess BOTH could be bad,, i mena the car is 23 years old.... Any idea?:bonkers:

The pulley to the left is an idler pulley I believe, and replacing it is usually the only fix. I bought mine at Advance auto. The other on you mentioned may be the air pump pulley. The tensioner pulley may have a left hand thread on it's bolt. I know the Chevy tensioner pulley does.