Under partial throttle, when easing up acceleration, I am getting a chirping sound like little birds. This does not occur when flooring the accelerator or under even somewhat hard, steady throttle. It does not occur on initial acceleration, but after throttling up to about 3000-4000 rpms, then a quick chirping, and then it goes away. My car is a 2003 MCS and has a 15% pulley and a 2% crank pulley. Crank pulley and new belt installed approximately one month ago. Any ideas of what this could be and a potential fix?

 

Sounds like a little slipage. When was the crank pulley installed? Same time as the belt?

 

Crank pulley and new belt installed at the same time.

 

I just started getting a chirping noise also. It sounds excatly like a bird in the bonnet. I have not done any pully mods but have put on the Alta CAI. I was thinking it might be an air leak in the intake system.

 

Hmm...I also have the Alta CAI