Whistle noise when under load

LukeH

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Sep 27, 2021
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10
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San Diego
I'm hearing a "tea kettle" type high pitch noise between 2k-3k RPM when I'm accelerating under load in 3rd, 4th, and 5th gear. I can control the whistle with the throttle meaning when it starts to whistle, if I give more throttle it goes away or less it goes away. It's right in the sweet spot of operating speed when going over 40 mph. There's no whistle when coasting at speed or when revving in neutral, only when under load. I don't have a throttle body spacer or an aftermarket intake. Could it be a vacuum leak or intake/exhaust leak even if it doesn't happen when not under load. It idles very smooth so I didn't think it was a vacuum leak but I'm not sure. I've also checked the drive shafts and they don't wiggle or have any play but I'm not sure if that means they could still need grease and if that could be the issue.

I'm fairly new to working on Jeeps so anyone who has experienced something similar and has advice or ideas, I would really appreciate it!

The Jeep is a 2003 with 51k miles

Thank you in advance!
 
If it does it when it's under load that usually indicates it's upstream of the throttle body. I had it happen once on a 300ZX after I rebuilt the motor and there was a crack in the rubber intake boot that connected to the throttle body.
 
I'm hearing a "tea kettle" type high pitch noise between 2k-3k RPM when I'm accelerating under load in 3rd, 4th, and 5th gear. I can control the whistle with the throttle meaning when it starts to whistle, if I give more throttle it goes away or less it goes away. It's right in the sweet spot of operating speed when going over 40 mph. There's no whistle when coasting at speed or when revving in neutral, only when under load. I don't have a throttle body spacer or an aftermarket intake. Could it be a vacuum leak or intake/exhaust leak even if it doesn't happen when not under load. It idles very smooth so I didn't think it was a vacuum leak but I'm not sure. I've also checked the drive shafts and they don't wiggle or have any play but I'm not sure if that means they could still need grease and if that could be the issue.

I'm fairly new to working on Jeeps so anyone who has experienced something similar and has advice or ideas, I would really appreciate it!

The Jeep is a 2003 with 51k miles

Thank you in advance!
I gave up on trying to figure out what it is. I have it too.
as for a tea kettle type high pitch noise, your spot on but its nowhere near as loud as a tea kettle. I mainly hear it when driving around with the radio off.

but its never gotten louder or gone away so I honestly just live with it.
 
If it does it when it's under load that usually indicates it's upstream of the throttle body. I had it happen once on a 300ZX after I rebuilt the motor and there was a crack in the rubber intake boot that connected to the throttle body.
Thanks for the reply! The air filter tube looks to be in good condition and I've tightened down the clamps but I'll check for any cracks on the tube or on the box.
 
I gave up on trying to figure out what it is. I have it too.
as for a tea kettle type high pitch noise, your spot on but its nowhere near as loud as a tea kettle. I mainly hear it when driving around with the radio off.

but its never gotten louder or gone away so I honestly just live with it.
Thanks for the reply and good to know I'm not the only one! And you're right, it's nowhere near as loud as a tea kettle, I say that just because it's the closest thing it sounds like.
 
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Thanks for the reply! The air filter tube looks to be in good condition and I've tightened down the clamps but I'll check for any cracks on the tube or on the box.

can you get it to do it intermittently by revving the engine? Maybe if you can get some help they can rev while you listen. Otherwise, it's probably gonna be a little tricky to find.

Vacuum leaks upstream of the throttle body often won't cause idle problems because since it's a speed-density system instead of mass flow, the flow is still unmetered at that point and won't affect the PCM calculations.

Other ideas - I haven't personally experienced any of these, just thinking through other items exposed to vacuum that could put air through a small orifice at speed.

IAC valves get dirty...usually causing idle issues but I can also see if deposits formed in the right way it could operate seemingly normally but cause air to whistle through it https://wranglertjforum.com/threads/how-to-clean-your-iac-idle-air-controller-valve.662/

crankcase vent system - runs from air filter housing to valve cover, then from valve cover to intake. On older models it runs into a nipple on the intake hose instead of to the air filter housing. the fittings going into the valve cover are notoriously brittle, and the rubber grommets they ride in harden over time. I would check the whole chain but particular attention on the end closer to the intake hose/air filter as that's the one that will see more vacuum under load than at idle.
 
If it does it when it's under load that usually indicates it's upstream of the throttle body. I had it happen once on a 300ZX after I rebuilt the motor and there was a crack in the rubber intake boot that connected to the throttle body.
Thanks for the reply! I’ve tighten the clamps on the air intake tube but I’ll double check for cracks.
 
My LJ does it too- noticed If you have a/c on and if you shut off while whining it goes away. Also moving throttle open or closed ever so slightly makes it disappear. Neither of my TJs do it.
 
If it does it when it's under load that usually indicates it's upstream of the throttle body. I had it happen once on a 300ZX after I rebuilt the motor and there was a crack in the rubber intake boot that connected to the throttle body.
Z31 or Z32? Both my Z31 and Z32TT whistled after swapping to cone filters.

Coincidentally... my TJ started whistling too, however after swapping to the THOR cowl intake (cone). Figured it was all related to the intake/filter design since I've had the same whistle across 3 vehicles.

(sure miss my TT!!!!)
 
@brewtus98 and @Mazepam, thanks for the comment. I tested how the whistle changes when turning on the A/C. Mine will whistle when the A/C is on or off but I just tried turning on the A/C while the whistling was happen and sure enough the whistle stopped for about 3-5 seconds right when I turned the A/C on before it started whistling again.

Given that the A/C has an effect on the whistle sound even though it’s only a few seconds, I’m wondering if maybe it’s something to do with tubing that’s connected to the A/C or if it’s one of the pulleys’ tension is effected for the 3 seconds that the A/C kicks on.

Anyone have any ideas now that the A/C effects the noise when turned on for a few seconds?

Thanks!