Having settled my transmission odyssey two days ago...

I noticed while driving that when accelerating, a noise (possibly a fan or belt) could be heard coming from from the left-most air vent. It only happened when accelerating, not while cruising or stopped. Interestingly, I could not replicate the nose with the noise with the car parked (in P or N). Turning the AC on or off has no effect.

I wondered if it was the serpentine belt, but I checked for that when parked, and could detect no hint of any unwanted noise when parked (I am familiar with that problem from a failed pulley bearing in my former x350).

Any thoughts?

 

Um, I think you're in the wrong section for this. Try the X308 section.
(';')

 

Hi Amelorn,

I've moved your post from the Off Topic forum to the X308 forum per your request.

Cheers,

Don

 

Thanks for the move Don.

Any ideas? I did some more "tests". When accelerating, the noise generally appears when revs are at or above 2,500 RPM. Having an idea, I decided to play a bit while cruising, shifting down to 3rd gear at 70mph for 5,500+ RPM. Despite the high RPMs, I could not replicate the noise when cruising.

Things I have ruled out:
-Serpentine belt & bearings - silent
-A/C fans (happens when system is off)
-Low oil (level is fine, oil is present up to the max dot; oil is 2 months/3k miles old)
-Weak oil pump (lack of any pressure warning)

Possibly...
5-30 oil is thick/noisy? Yes, I am grasping at straws.

I am going to have a new pair of front shock mounts installed in the next couple of weeks, so I may put the shop on the case.

 

With the bonnet open and somebody hitting the gas, can you hear the noise in the engine bay.

Over the years Somethings I remember seeing: slipping/flopping belt; loose primary and secondary tensioner chains; bad VVT (not your problem); loose power steering pump; loose spark plugs (my case). Last two gave a buzzing sound.

Since it does not reflect change in ac status, not likely something jamming up the ac vent.

Never paid attention to issues specific to super chargers, but that may be where you need to look.

 

Jhartz, my engine is N/A, not supercharged. The VVT is in play

So I got my friend to lend a hand. We took took turns revving and listening.

The noise that concerned us was not anything we heard revving up (circa 2500 rpm), but what we heard on the engine returning to idle (650 rpm) after taking our feet off the accelerator.

There was a click and a noise that repeated 5 times in rapid succession as the car went back down to idle. It appeared to be coming from the front & top of the engine and just behind the serpentine belt.

I've attached a 40 second audio recording. The first 6 seconds give you a "baseline" of the engine at idle. Listen to 25-35 to hear the click + 5 mentioned in the prior paragraph.

Thoughts? The car is running on 5-30, and I am wondering if a can of Restore may be in order, as I suspect that I am dealing with VVT noise.

Edit: No codes are present.

 

Sorry, I thought the sport was supercharged. Sounds like VVT, might also use a stethoscope and listen along the fuel rails for a sticking injector.