Whistle!

I need some help. My wife and I just bought a pre-owned 08 Jeep Grand Cherokee with about 60,000 miles that just started to make a whistle sound on initial acceleration and deceleration when the engine is warm and the transmission is in gear and moving. The sound does not happen with a cold engine, when the transmission is in park, or neutral. A local mechanic checked it for vaccum leaks and didn’t find any. He thought it may be a diry throttle body, so I cleaned that out really well, but the whistle didn’t go away (it did make the jeep run a lot smoother!). It’s difficult to pinpoint the noise since it only happens when the vehicle is actually moving.

Any help or suggestions would be greatly appreciated! It’s only annoying right now, but I want to make sure it’s not indicative of some major issue.

Does it whistle at a steady speed?

No. It’s more like a low range rpm…2000-2500. On acceleration I can sort of make the sound go up and down or even sustain it for a bit with a very sensitive push/release of the gas pedal. On deceleration, it just happens on it’s own around 1000-1500 rpm.

Also, forgot to mention previously that the whitstle only happens on acceleration from a complete stop. It happens every time I stop when the engine is warm.

Does this vehicle have the factory air cleaner?

Thats a vacuum noise…you need to go back over ALL the vac lines in your system… They missed something… If you want to do the test yourself…see if you can find the general area of where the sound is emanating from…THEN…grab a can of WD-40 or other spray lube and spray wherever you hear the noise…if it goes away or stops with the spray…YOU FOUND IT… Best I can tell you to do…Its a pain in the ass but be diligent…you can find it… just be patient

Over the years I have become a sort of Savant in finding where these issues come from… Takes time patience and practice…just like anything worthwhile I guess

Blackbird

I’m going against the grain here. I think its an exhaust leak, not a vacuum leak. The leak could be a cracked exhaust manifold, the exhaust manifold gasket or the doughnut gasket between the exhaust manifold and the exhaust pipe.

If you have a warmup cat, it might be the seal around it.

Yea could be that too Keith… Now you have two homework assignments… Look for Vac leaks as well as exhaust… Exhaust usually dont whistle tho…but a good thing to check nonetheless

An exhaust leak that whistles is rare, but not unheard of. When it does occur, it usually occurs on acceleration only, but it can also whistle on deceleration if there is enough overlap on the cam profile to allow a vacuum to develop in the exhaust manifold during deceleration.

A leak on the intake side usually will whistle more at idle and deceleration than acceleration, however, it could be whistling above the hearing range and becomes sonic only during acceleration.

Wow, thanks guys! I have lots of homework to do. I’ll get cracking and let you know what I find.