I immediately noticed, however, when I am accelerating above 1500rpm's, I can hear (with the windows down) a loud hissing sound which gets louder the more I accelerate. The hissing sounds like a turbo spooling up.

I checked to make sure that there are no pinched hoses from the intake and everything was reinstalled perfectly. I have a K&N cold air kit on the car. I just thought this noise was normal and didn't really think too much about it, but I now worry a bit that something may be choking. Has anybody else experienced this? Does anybody have any suggestions as to what could be making this sound?

I have another un-related question for anybody who has the K&N cold air kit installed. On the bottom of the intake tube around the filter end there are two hose outlet grommets. I only have one hose physically connected because I didn't have another to hook up. Is there supposed to be two hoses hooked up to it? What is the second (larger) hose for? Is this a hose used on other R50 models? I currently have the larger grommet plugged up.

Here's a couple of pics of what I'm talking about from the installation guide:

Thanks!


Modified by Pwnin O'Brien at 12:42 PM 7/4/2009

The only thing that comes to my mind, is a loose connection (especially if you removed the throttle body) and air is hissing out (like whistleing)

PS - How do you like the intake? I've been debating this... is it worth it?

I love the intake, I don't really notice the horsepower gain (something like 14.4hp in the 5000rpm range) but it makes my truck sound awesome. During acceleration it sounds really good.

I googled the issue, and came up with nothing.

Did you completely disassemble the tb?
Maybe just for good measure, take it off again and double check your work.

I'll keep looking into it and let you know if I find anything.

I'll replace the gasket and post my findings.

P.S. I also e-mailed K&N Tech support to find out about that hose and they haven't gotten back to me but I'll post their response when they do.

Let me know what K&N has to say.

Thanks for your help!!!

So the hissing that I originally thought had disappeared had not actually disappeared. I have had the hissing noise for the past 8mos. or so, I just ignored it. I recently had to remove the intake and throttle body to do the throttle body bypass and I figured this would be a great time to get rid of the hissing for good. My solution was to use some RTV gasket maker instead of the gasket from the dealer. The gasket maker went on well and there were no visible gaps. Once I put everything back together and revved up the engine to test for the leak I couldn't hear any hissing anymore, so I figured I fixed the issue.

Well, when I started to drive the vehicle I noticed a new sound. There is a louder whistle coming from under the hood, but this whistling is different from the last one. The last whistle would get louder as the RPM's increased, sounding like a vacuum leak. This new whistle is not dependent on RPM's, it is dependent on the accelerator pedal position when the engine is under load (the issue does not happen with the vehicle in neutral). When I hold the pedal in a certain position the pitch of the whistle will change, as I push the pedal a little closer to the floor the whistling gets deeper and then goes away as I push the pedal further. The whistling sound only happens when the pedal is at this specific position. There's a very small amount of pedal travel in where it will make this whistling sound. The whistle is so loud it can be heard very easily in the cabin with the windows up.

At first I thought maybe the throttle body cleaner I used to clean the throttle body before re-installing it may have somehow fouled up the electronics in the throttle body. I don't have any DTC's but I doubt I have driven the car enough to register one yet. Also, I listened to the throttle body during the power-down cycling (when you turn the vehicle to OFF the throttle body will cycle completely). I heard not strange noises when it cycled so I am assuming it isn't the throttle body electrical motor.

I thought maybe it could be a different vacuum leak but what vacuum changes with the accelerator pedal position? I could see it changing with the engine RPM's but not with the pedal position.

I really have no idea what this noise is and I could really use some help with this one. If anybody has any ideas please let me know, I'm up for anything!

its the sound of the air hitting the butterfly.

mine makes it very quietly (cant hear from the cabin) but ive heard cars that have it very loud. Thats why stock intakes have a (restricting) airbox before the filter - to muffle the loud sounds from the intake (at the cost of losing power)

See, I heard that a lot with the R51 Pathfinders but I haven't heard of anyone having problems with the R50 throttle body. When you put it back on, what were the symptoms of failure? Did you get the SES light or was the TB making any strange noises or did it just stop working completely?