AWS82

I have a 2009 Cayenne GTS with 68k miles. The temps have been up and down in the D.C. Area and last week, when it was around 27 degrees, I noticed a "flutter" noise coming from the lower part of the engine. You can really hear it by the driver side wheel well, it's louder in the morning when the engines cold. When I pull out of the driveway, it's pretty noticeable but it goes away if you throw it in neutral. 1. It's noticeable when I accelerate 2. It's noticeable sometimes when I'm slowing down. Any ideas??

nodoors

I can't listen the to the video right now, but I would check the AOS first. They can make a fluttering sound when they tear.

nodoors

It is really difficult to tell what is going on there. I don't hear fluttering so much as an irregular idle or missing sound. It does not sound too much like an AOS, though.

Can you get a longer clip with the hood open with the engine idling and then rev it up and hold the revs at a few different rpms?

Petza914

I hear what sounds more like a knocking than a fluttering, but maybe I'm not hearing the right sound. Think we need a better and longer clip, as mentioned.

deilenberger

I hear what sounds like a mechanical noise - either a noisy lifter or a noisy injector. Direct injection does tend to be rather noisy.. (I'm actually a tad surprised Porsche didn't try to damp out the injector clatter with some sound damping under the beauty covers on the engine.. or underhood damping.)

nodoors

It is a noisy engine, but the worst sounding one of recent times to my ear is the 4L V8 in the 2012 M3. At idle it just sounded like 10 people playing the maracas riding around in an old farm truck (and accelerated like one) - until it revved past 5-6k rpms!!! Then it started sounding beautiful and making some power.

Andy E.

This sounds like engine detonation or knock; caused by either low quality fuel or bad plugs. The noise and frequency will be more pronounced with warmer weather and usually occurs at low RPM and under load.

When were your spark plugs replaced? What type of fuel do you use?

AWS82

*UPDATE
So the noise you were hearing was a leaking secondary cat. Replaced exhaust manifold gaskets ($2000) and installed a resonated secondary cat bypass ($800). "Flutter" noise gone. Initially, I thought it may have been the coils but it wasn't. However, they needed to be replaced anyway.

Before I had the gaskets replaced and secondary cats switched out, I went ahead and:
1. Replaced the coils/plugs - BERU coil pack (8) and BOSCH OEM plugs (8). I got them at partsgeek - $450 for it all ($1100 total w/labor)
2. Changed the oil, Mobil 1 0W-40/K&N oil filter
3. Flushed and replaced PDCC reservoir (routine at the 60K mileage mark)
4. K&N air filters ($120)