2004 Jeep Gr Cherokee Laredo - 4.0L Whistle

[92zman]

We have a 04 jeep here that has a whistle coming from under the hood at idle. Put on a PCV hose still doing it. Thought then it might be the iac motor but seems to do it when it is at diffent point of it travel. Comes and goes if i go out and drive it it will start doing it again but when i get back in the shop it will stop after a bit ..

[ricmorin]

There are three different engines on a 2004. Which one do you have?

[92zman]

sorry it is 4.0 6cly

[liljoe]

Drive it with the oil cap removed and see if the noise still happens.

[92zman]

took off oil cap still did it. It will make a higher pitched whistle while driving down the road at about 20% tps

[Tim Martin]

Carefully check each vacuum hose. Another thing I have seen on this motor is vacuum leaks at the intake manifold gasket. I use 2+2 Gum Cutter and spray at the gasket area. If there is a leak, the engine rpms will change.

[steven kiser]

i agree with the vac leak. i've done more than a few intakes on these. the intake bolts on these have a habit of backing off or breaking. the other thing i've seen is the iac will sludge up and needs to be cleaned. the point will have a buildup that you will probably see a space on and really clean the seat well. you make have a stall issue when you're done and need to perform the monitor reset procedure. when i have a noise and spraying with carb cleaner doesn't seem to work i'll use a piece of 3/4 inch heater hose to listen. it will help isolate the area. put one end to one ear and roam around the engine with the other like a stethoscope.

[ricmorin]

If there is a vacuum leak it should show in the fuel trims. Are the trims ok?

[92zman]

checked all vac and gaskets all seem good. Fuel trim is good.

[steven kiser]

i'd look into the iac. i've also had alternators make a whistling noise.

[Tim Martin]

Ah yes. Forgot bout the alternator possibility. I also seen that already.

[steven kiser]

maybe if i know the tune i can hum along. sorry, it just seemed to fit so nice........

[Tim Martin]

maybe if i know the tune i can hum along. sorry, it just seemed to fit so nice........

ya gots yer imagination werkin overtime steve!

[steven kiser]

got to get all my unused steveisims out before the end of the year. i hate carrying baggage from year to year. if you can't laugh at yourself then you're missing a lot of laughs.

[Tim Martin]

Having a good sense of humor helps in this business. retains my sanity and makes my customers realize I do have mental and emotional limits.

If I am not careful I'll get this thread off the initial subject though.

[steven kiser]

ya, that will really piss me off