I have a 2000 TJ, 6 cylinder. It runs great but the past month or so there has been a whistling noise under the hood. Any time I let off the throttle it makes a whistling noise.... When I let off during shifting or going to a stop it happens, but once I get back on the throttle it stops... Any ideas on what it could be?
You have a vacumn leak, check all your vacumn hoses for being loose, cracked, split if you don't see anything obvious retorque your throttle body and intake manifold bolts. If its still there you can use a stethoscope with end pulled off to search for it.
I thought it might be a vacuum leak, but I checked all my hoses and didn't see any real obvious damage. I also couldn't justify why it only happens when I let off the gas? I am familiar with exhaust leaks and it doesn't sound like that... It almost sounds like a bearing, although I'm hoping its not because that means alot more time and $$$!