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Hey there,

Was hoping someone could point me in some direction. I've got a 2013 Pro-4X (6-cyl) manual transmission. I've got this subtle sound the seems to "turn on" at exactly 2250 RPM. The best I can describe it is it either sounds like a faint exhaust leak, or like a fan is running and something hitting the blades. It's very faint but over time it's starting to irritate me.

So I was wondering if something "turns on" at that RPM speed, like a fan or something. Here are some additional observations.
* It happens in 1, 2, 3 gears, can't tell if it does in 4, 5, or 6 because the cabin is too loud at that point.
* It does *not* happen if I just rev the engine up to that RPM speed with the clutch disengaged. Only happens if the truck is moving. Sounds goes away when I let off the gas. Sound persists if I keep a constant speed around that RPM.
* It does not happen when it's cold. Takes a few miles before it starts.
* Like I said it's very soft, if I roll down the windows and stick my head outside I can't seem to hear it. I can't tell if the sound goes away as the RPMs climb or if I just can't hear it over the engine noise.
* It sounds like it "turns on" all of sudden. It's not a gradual build-up.
* When I start the truck, the cooling fan starts at full blast and then slowly settles down. I've heard that's a faulty fan clutch. Wondering if that's normal or related or another issue.

Any ideas?
 

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There was a TPS about something in the intake track that would rattle at about that RPM. Mine does it some times. THe fix was to pull it out and epoxy it in place. Other than an annoyance, I didn't recall that it was a detriment.
 

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I've heard of this issue but never heard it in my '10 Pro-4x 6spd. I've heard the fan on start up a handful of times on very hot days which makes sense.
 

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Its the Variable Air Induction (or Intake?) System, VAIS. Its a valve in the intake manifold that closes between around 2200 through the high 3,xxx range. It's to increase the torque output in that RPM range.

Many years ago I bought this article from SAE where I learned about this system. Development of a New 4.0L V6 Gasoline Engine Kinda pricey but interesting read.

My 06 has this sound as well. I ended up replacing the VAIS valve at around 150k miles, (was like $50 and took like 15 min to do), and the sound went away complete. Now I've got about 160k miles and the sound is back, but no where near as bad as it used to be.

There is a TSB on here documenting a procedure on epoxying the VAIS valve so it wouldn't flutter anymore, but I was not about to put epoxy on something going into my intake manifold!

And fun fact, have someone step on the throttle and you can see the linkage close the valve when it hits 2200 rpm.


Anyways, the sound is harmless. So either try live with it, or replace it, however the sound most likely will come back at some point.
 

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Its the Variable Air Induction (or Intake?) System, VAIS. Its a valve in the intake manifold that closes between around 2200 through the high 3,xxx range. It's to increase the torque output in that RPM range.

Many years ago I bought this article from SAE where I learned about this system. Development of a New 4.0L V6 Gasoline Engine Kinda pricey but interesting read.

My 06 has this sound as well. I ended up replacing the VAIS valve at around 150k miles, (was like $50 and took like 15 min to do), and the sound went away complete. Now I've got about 160k miles and the sound is back, but no where near as bad as it used to be.

There is a TSB on here documenting a procedure on epoxying the VAIS valve so it wouldn't flutter anymore, but I was not about to put epoxy on something going into my intake manifold!

And fun fact, have someone step on the throttle and you can see the linkage close the valve when it hits 2200 rpm.


Anyways, the sound is harmless. So either try live with it, or replace it, however the sound most likely will come back at some point.

Thanks for this. I always thought my "buzz" was this too. So I am not too concerned. But when you are pulling a load over the pass, and your truck is buzzing away. It does raise your blood pressure some. I should look into getting a new valve.

Do you have a copy of the paper you can post as a PDF or send it to me ([email protected]) . Those funny file types are not working for me.
 

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<.....>Many years ago I bought this article from SAE where I learned about this system. Development of a New 4.0L V6 Gasoline Engine Kinda pricey but interesting read.<.....>
thanks for the reference. I see that this is available nearby at the Univ of WA so I'll head there to take a look at the 9 page article.

update: i didn't even have to leave my chair ! I sent the Seattle library "Interlibrary Loan" dept a request for the report and within 24 hrs they provided me with the document and charged my library card a few dollars wow
 

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At ~25k right now. I listened very carefully for this yesterday...could not detect anything. Should I expect to hear this as the miles increase??
 

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Its the Variable Air Induction (or Intake?) System, VAIS. Its a valve in the intake manifold that closes between around 2200 through the high 3,xxx range. It's to increase the torque output in that RPM range.

Many years ago I bought this article from SAE where I learned about this system. Development of a New 4.0L V6 Gasoline Engine Kinda pricey but interesting read.

My 06 has this sound as well. I ended up replacing the VAIS valve at around 150k miles, (was like $50 and took like 15 min to do), and the sound went away complete. Now I've got about 160k miles and the sound is back, but no where near as bad as it used to be.

There is a TSB on here documenting a procedure on epoxying the VAIS valve so it wouldn't flutter anymore, but I was not about to put epoxy on something going into my intake manifold!

And fun fact, have someone step on the throttle and you can see the linkage close the valve when it hits 2200 rpm.


Anyways, the sound is harmless. So either try live with it, or replace it, however the sound most likely will come back at some point.
Thanks for the information. That electronic, computer gizmo stuff, I am clueless!
 

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* When I start the truck, the cooling fan starts at full blast and then slowly settles down. I've heard that's a faulty fan clutch. Wondering if that's normal or related or another issue.
My fan clutch did this too. Its a fluid filled clutch, and I think on starting sometimes the clutch is "stuck" and fully engaged until a few revolutions where it will properly free up.

My clutch did fail at somewhere around 120k miles. It basically would just stay at full blast. It sounded like a Mack truck when you hit the gas. Ended up replacing that as well. So I'd say your situation is normal.

Do you have a copy of the paper you can post as a PDF or send it to me ([email protected]) . Those funny file types are not working for me.
I only have a paper copy around with me and unfortunately my name is plastered all over it due to SAE's copyright stuff.

At ~25k right now. I listened very carefully for this yesterday...could not detect anything. Should I expect to hear this as the miles increase??
Hard to say, but I would say there's a good chance it could happen in the future. I bought my truck used with 10k miles on it and I didn't start hearing the noise until after 100k, don't remember exactly when. The noise isn't exactly loud , its kinda like a buzzy/gargle type nose under load that occurs just as the rpm passes around 2100 rpm when the valve moves.



Heres a few old threads on the topic:
http://www.clubfrontier.org/forums/f11/vias-delete-verified-hp-gains-losses-61088/
http://www.clubfrontier.org/forums/f8/rattle-under-acceleration-82898/index2.html
SOLVED: Engine Rattle at 2200 RPM - Second Generation Nissan Xterra Forums (2005+) -Page 3 has pictures of the valve
 

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I just wanted to follow up on this. I found TSB NTB05-015b "RATTLE NOISE FROM VIAS POWER VALVE ACTUATOR / INTAKE MANIFOLD COLLECTOR" on the Internet somehow and followed the instructions and it has solved the problem. You have to get three things: special epoxy, an applicator and a mixer nozzle. The applicator is expensive but I found a used one on Ebay for cheap. I did the procedure and let the truck sit overnight. No more annoying noise.

Many thanks for the helpful pointers.
 

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Thanks for following up not leaving us hanging.

Clint
 

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I just wanted to follow up on this. I found TSB NTB05-015b "RATTLE NOISE FROM VIAS POWER VALVE ACTUATOR / INTAKE MANIFOLD COLLECTOR" on the Internet somehow and followed the instructions and it has solved the problem. You have to get three things: special epoxy, an applicator and a mixer nozzle. The applicator is expensive but I found a used one on Ebay for cheap. I did the procedure and let the truck sit overnight. No more annoying noise.

Many thanks for the helpful pointers.
Thanks for this. On what yr Frontier did you perform this repair?
 

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At ~25k right now. I listened very carefully for this yesterday...could not detect anything. Should I expect to hear this as the miles increase??
My '06 6-Speed has 151,000 Miles on it now and I've never heard any of this, and I'm pretty sensitive to noises. I think the VAIS TSB was directed mostly at early production 2005s.
 
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