One thing about pulleys is that it should also make noise even when the vehicle isn't under load. Just revving the engine while the vehicle is in park or neutral should still make the noise. I have seen some weird things so it's definitely possible. A good check is to remove the belt and spin the pulleys by hand. It should spin freely without noise and a "rough" feel. Is the belt glazed (shiny spots on the ribbed sided)?

 

I definitely agree with you. It seems that the sound would be constant if it is the pulley, and this sound is intermittant. I figure it wouldn't hurt to replace the pulley and belt, and if that doesn't fix it, I'll start going through the air and vacuum system closely.

Micah

 

Good luck and hope you find/solve the problem! If I think of anything else I'll be sure to post.

 

Do you have a CAI? The whistle is coming from your throttle body. All of the jeeps do it to a point but you really cant hear it that much unless you put a CAI on it. My neighbor does not have a CAI on his and his has a slight whistle also.

 

I know some reported a whistle after installing a throttle body spacer. I would double check the throttle body bolts. The fact you hear it under throttle sounds like an intake issue.

 

that's the noise i have... hasnt gotten worse in 10k miles, dealership hears it but cant figure it out either.

 

I found that if its the tensioer, the sound will get worse over time to the point that it does make noise even sitting at idle. At first, it was a low whistle but was totally fine at idle. Aftetr about 2 weeks.....awful.

Hopefully you will find the issue and fix it regardless of what it is. If you've been in any deep dirty water latley, I'd put money on the issue being the pulley. If not, hopefully one of the other suggestions help!

Good luck!

 

I don't have a CAI or throttle body spacer. My initial impression was that it was an intake or vacuum issue, but I haven't been able to find a cause. I'll check the bolts this evening to see if that might be a cause.

Thanks for your help guys!

Micah

 

Had a similar issue on my 330i a couple years ago. High pitch whistle that was seemingly dependent on throttle position. Ended up being a crack in the intake tube just before the TB. I know you've already checked it but it sounds like you could have a very slight crack at the bend.

 

My jeep made a whistle when I smashed my exhaust. The engine would wine when driveing on freeway around 60mph. Probably not your issue but a quick look wouldn't hurt.