I have a 2006 Camry 2.4l and I'm hearing a loud noise coming from the idler pulley on cold start ups when I put it in gear. I don't hear it when it's in park. The noise gets worse if you turn the a/c on. I have replaced the belt, idler pulley and top motor mount. I took the belt off and cranked it when cold and there was no noise even in gear. I can see the idler pulley moving and can confirm that's the noise but what it causing the belt to make it do that? Has anyone else had this problem? Could I have bought a defective idler pulley?

 

"Idler pulley moving" as in rotating?

Have you used a section of hose as a stethoscope to confirm the location and even area of pulley making the ?

Is the idler pulley lined up with the rest of the pulleys and not causing the belt to be pulled one way or the other?

 

The belt has a small wobble to it but the noise is definitely coming from the idler pulley. I can see it making the noise lol. If the the belt is misaligned, how can I align it?

 

The belt has grooves in it that should line up with grooves on the pulleys.
I would start by removing the belt altogether. Examine all the pulleys. Make sure that all pulleys that should move freely, do. Make sure everything is tightly mounted, like the alternator bolts aren't loose or anything like that.
If everything looks good, reinstall belt and make sure that it is seated properly into the grooves.

 

Yes I have done that. I see a little bit of side wear on the belt but not much. It seems close to the left side of the a/c pulley. I just don't think there's any way to move any of the pulleys to align it better

 

Is the wear on the belt all around that side or is it in spots?

 

Spots

 

Spots makes me think that something might be bent and not quite true.
Here's what I would do, start the car, VERY CAREFULLY take something like a ruler and put it against something like the wheel well with the other end close to one of the pulleys, hold the edge steady and compare it to the turning surface of the pulley. You should see any irregularities or wobble. Again, please be careful if you try this.

 

The noise stops when the car is warmer though. If it was not true wouldn't it get worse at higher rpms?

 

If the spots are friction points, then there is heat generated at those spots. The belt is made of rubber which will soften when heated up. The soft spots are less apt to make noise, etc.
Softer rubber also makes it grippier.
This is kind of hard to diagnose over the net but I'm doing my best