A couple of weeks ago I got back from vacation and when I started my car up it was idling higher and there was a sound coming from one of the pulleys but I couldn't tell which one. After I drove it for a couple days the sound went away but it was still idling high. If I drive it for a while the idling goes down but it still says check engine. I went to get the code read today and it came up with p0172 and p0175 which it said was to rich (bank 1&2). I was thinking O2 sensors but since I heard a noise from one of the pulleys I'm thinking that's it. I don't know which pulley it might be or if that's even the problem. Any ideas?