Possible Vacuum Leak?

[RockstarBobby]

Alright Jeep Family - I've got a head-scratcher going on over here. Not sure if it is a possible vacuum leak or something else. Could use your collective input.
Possible Information Needed:
2003 TJ Sport, 4.0L, Automatic, 121k mi
Banks Cold Air Intake
Throttle body spacer
Standard OEM Throttle Body
(Let me know if you need more info)

This noise has happened intermittently. Sometimes I hear it at idle, but mostly I won't hear it on initial startup & idle. I hear the noise once the engine gets to temp and I grandma drive it through my small town going around 20-35mph. I have also heard it going highway speeds - but not as loud or as often. As soon as I give it a touch more gas or let off the gas - the noise goes away for that split second, but if i feather the gas pedal - the noise comes back.

I removed throttle body spacer- no change. Noise is still there.
I checked the belt and it looked brand new.
I looked at the pulleys - and by look I mean I let the engine idle and didn't see anything out of the ordinary at idle or when I used my hand to rev up the engine.
Interestingly enough - this noise was not noticeable while looking/listening under the hood - but in all fairness, my hearing is not the best.
I couldn't see any cracks or loose vacuum hoses/connections - but I am uncertain if I may have missed any.

I took this video from the inside of the jeep while trying to recreate the noise so I could get some help from y'all. Take a listen and let me know what you think.

Currently - jeep is at the shop getting new gears/lift/and steering work completed - but I did ask them to take a look too.

 

[Chris]

Video doesn’t work, it says we don’t have access. You must have set it as private.

Have you performed a smoke test to see if it is indeed a vacuum leak?

 

[RockstarBobby]

Video doesn’t work, it says we don’t have access. You must have set it as private.

Have you performed a smoke test to see if it is indeed a vacuum leak?

Hey Chris! Fixed the video so you can hear (see) it.

I haven’t performed a smoke test before. How do you do that?

 

[Chris]

That's really weird. It definitely could be a vacuum leak though, no doubt about it.

Here's how you can build a cheap smoke machine and do a smoke test:



This is nice because it will allow you to find vacuum leaks that may be invisible to the naked eye and near impossible to find as they are hidden / tucked away.

This is where I think I would start at least.

I find it odd it's not throwing and codes, because running like that it should be.

 

[Flivver250]

Clips of noises coming through computer speakers aren't a good replacement for actually being boots on ground at the scene of the crime. It could be vibration resonance from something loose or possibly a vacuum leak, but leaks should throw a code I would think. Your throttle body spacer isn't helping anything, but probably isn't causing a noise.

 

[RockstarBobby]

That's really weird. It definitely could be a vacuum leak though, no doubt about it.

Here's how you can build a cheap smoke machine and do a smoke test:



This is nice because it will allow you to find vacuum leaks that may be invisible to the naked eye and near impossible to find as they are hidden / tucked away.

This is where I think I would start at least.

I find it odd it's not throwing and codes, because running like that it should be.

I know, right! It is super weird that it doesn’t throw a code at all.

I like this smoke test set up. Seems like it would a great tool to use. Definitely going to try this out if the shop doesn’t find the leak.

Thanks for the info!

 

[RockstarBobby]

Clips of noises coming through computer speakers aren't a good replacement for actually being boots on ground at the scene of the crime. It could be vibration resonance from something loose or possibly a vacuum leak, but leaks should trow a code I would think. Your throttle body spacer isn't helping anything, but probably isn't causing a noise.

I was hoping someone might’ve had a similar issue and could hear it on the video - it’s a long shot I know. I’ll try this smoke test. Maybe a manifold is loose or a gasket failed? I would think that would throw a code though. it’s a real gremlin.

 

[Chris]

I know, right! It is super weird that it doesn’t throw a code at all.

I like this smoke test set up. Seems like it would a great tool to use. Definitely going to try this out if the shop doesn’t find the leak.

Thanks for the info!

Yep, that is indeed a great tool to have handy.

Try it out and let us know what you find