CHRONIC_2001_XJ

This is driving me nuts! I'm getting a high pitched whistling noise coming from my engine that I can hear inside when I'm driving. It only happens when I'm moving and when I let off the gas. Just the slightest bit of pressure back on the gas pedal and it goes away.

The problem is that it only happens when its moving so...I can't inspect where the sound is coming from.

I posted about this a while back and some recommended to tighten my intake manifold. I did that but it still does it. Any suggestions? Thanks!

ZINGGG

I've read that a vacuum leak can cause i whistle. However I have no experience with that so I can't tell you firsthand. So check all your lines

soundrew

I have the exact same thing. I've changed some vaccum lines but it still is happening periodically. Let me know if you find an answer.

car5car

compressor clutch can whistle

00jepxj

i think i got the worst wistle it only did it when warm like 220 in the trails now its all the time on the high way or at red lites i noticed a hising noise from my brake booster changed it got better but its pissin me off i taking off to maine friday i wanna fix it my engine lite says large evap leake i followed every line nothing my bottom end makes a lot of vacum could it be bad pcv or somting like that once in a wihile it spunds like a bollon with the end pulled flat ...

UJSLOST

check vac lines at charcoal canister

brg0012

Do you have any type on intake modification?

00jepxj

sorry i not trying to seal this tread but i took off stock air box and put on a filter on the tb but it did it befor that

UJSLOST

Not running a stock air box will give a whistle sound.

fishtaconc

X2^... You didn't by chance have the TB bored? Also, when I first got my 99, it had a whistle, and the TB was dirty not allowing the butterfly to close just enough, but it had a little higher than normal idle too.

maddogs1965

I had a whistle when the cold idle would kick down, and ONLY when i let of the gas pedal no matter if i was driving or just sitting there idling....It also drove me crazzzzzyyyyy...

I had a mechanics stethoscope, and it sure sounded like it was the #5 Injector O ring sucking air from the head side. So i changed out all the Injector seals and fuel rail seals, fired it up, and as soon as the cold idle kicked back down, there was the whistle again

So this time i grabbed a can of brake clean with the little plastic nozzle on it that would shoot a stream of brake clean, and started to hit the intake gasket were it met the head with the motor running. If you have a intake leak the idle will go up when the motor sucks in the brake clean. (or anything else flammable)

Turns out very back bolts that hold the intake/exhaust gasket to the head had loosened up, and thats what was causing the whistle. So i managed to get a open/box wrench on all the bolts, and tightened them all up....

SUCCESS....the whistle went away, so maybe its too late for your intake gasket, and you need too change it out if you already tightened the bolts, but try the brake clean first too see if you have a intake leak...

CHRONIC_2001_XJ

Thanks....I will try again and double check back bolts as well as shoot some break cleaner around there.