Mine whistled a lil too not nearly as loud as your talking about but what I found was a disconnected CVC tube. Air was being pushed through it and making a whistle sound like a boiling tea kettle.

You could look in to that also.

darn renixs lol

I'll look into the cvc. where is that thing located...or will it show in a chilton manual? Or do you mean CCV crank case ventilation system??

They are just the lil tubes going all over the throttle body I had one that came loose is all. I don't know what they are all called and stuff.

But we sprayed either all over the place to see if the idle went up but no such luck. I'm thinking vacuum to something else or bearing on the front of the motor. I just wish it would go away for him, since he is so annoyed.

Have you checked your idler pulley (The pulley that does/runs nothing)
Its the one in the center that pushes DOWN on the belt.

Loosen the serpentine belt and slide off.
Try spinning it. Should spin freely, with a very slight bit of drag.

With it being a 95, I would almost bet it needs replacing.

His jeep is a 2000, but it does have around 170 or 180K on it. We haven't checked it yet, he is being stubborn and saying its in the back so It looks as if I am going to have to try it for him. I also want to know what it is an that is an easy "try".

Funny - I've got the same problem. I thought I wouldn't see anything on this but here it is. I have a 2001 Cherokee bone stock except for the 3 inch lift. Mine started about a 2 mos. ago. It starts fine, runs great then starts whistling when it warms up and I'm driving above 35. If I stop the car it goes away after a short while. If I'm driving in slower traffic for awhile it goes away. Oh and when I accelerate it disappears and comes back when I release the throttle. What gives? Any help would be great!!

Ben

sounds like your idler pulley cause mine was doin the same and thats all that it is but its a super easy fix there is just one bolt that holds on the pulley

OK, seems we have come to and end for the most part. My brother took his cherokee into the mechanic and they told him it was the valve cover vent. You know that other PVC looking thing on the back of the valve cover that goes to the intake. Fixed the noise for a day, hahahaha but we have came to a headway here. Today while at work I was poking around under the hood and low and behold I wiggled something that didn't like being wiggled because the noise changed tone and then stopped. The piece I wiggled is
...........drum roll...........the vacuume hose running to the brake booster! Now I'm not 100% positive that this is it but dang sure. I'll let you know if thats the complete fix.

Hose clamp it.

Cant hose clamp it because its the part that goes into the booster itself, but the good news is that it hasn't whistled once since I wiggled it.

well i have the same problem and mine is deffantly the idler pulley i just haven gotten around to replacing it yet. but its deffantly the idler, beacsue it started just last week by squealing then whistling, now its a loud grinding noise, sounds like metal on metal ball bearings to me. i have 156k miles on my 99 and i go through alot of mud and high water so that would make sense that the bearings would go.

My wifes 01 is whistling now,145k miles, 4.0 auto, 4wd. It starts after we have driven it for at 30 to 45 minutes when we let off the accelerator, hit the gas and it goes away. I have not been able to get it to do it in the driveway so it's hard to diagnose. At least now I have a few things to check.

Well Folks, It went back to the shop because that wasn't the fix. Turns out it was a leaky intake manifold gasket. When you accelerate it went away and during deceleration it was whistling. Must have been just the right size leak to make that noise. Been driving it for 2 weeks now and it has finally stopped.