lyleswk

Well, reading this thread this morning, something very different pops to mind and reminds me how difficult it is to diagnose things with descriptions on a computer screen since most of our brains go the direction they are aimed during the initial comments. Anyway...

For some reason this morning, all I could think was driveline, specifically axles. Did you grab the front axles and shake them to see how lose they were?

03_AR_CO

+1 as something to check into, inner cv joints can make a racket, and will sound different under load vs coasting. Worthwhile checking into IMHO.

kjmiles

Axles and inner CV joints? Interesting. When we put the car up to take a look/listen underneath, we didn't think of these components. My friend Jeff and I thought it sounded like it was coming from up higher. It definitely is related to load/acceleration though. If you're driving 70 and push in the clutch, it goes away. So that would seem to nix those ideas. I appreciate the thinking and collaborative problem solving still waiting for a call from shop #4.

DKoehne12

I have kind of the same thing coming from mine. It sounds like its coming from my turbo and it only happens on acceleration. I checked all my hoses and everything. It sounds like a bunch of air is being pushed out somewhere for me. i feel like I lose a lot of power when this happens. I just noticed that on my way home tonight that it didn't do it and I had a ton of power again. I thought maybe my turbo was going out. I really don't know what it is though. I'm in the same boat as you. I have a 2004 A4 Quattro 1.8T

DKoehne12

My noise came from the Pressure check valve. It is located on the drivers side near the firewall. Part number is 058 133 753B. Mine came apart and it was doing all that now i fixed it and it is working great now. No power lose and no noise anymore

kjmiles

That's good to know. I had read up on the same thing. The PCV seems to be logical. Did you replace it yourself? If so, is it difficult to do? Long, long story short, I had this retired Audi "expert" (whatever your definition is) do a lot of diagnostic stuff on my car. We drove around with his computer hooked up taking readings. He recommended that I replace the thermostat, change my oil more often (I do it religiously around 3K), change the right engine mount and snubber, change the valve cover gasket and chain tensioner gaskets (my mechanic tells me this is pretty much normal wear and tear now every 3-5 years!), and do the catalytic converter and the pre-cat oxygen sensor. My mechanic, who knows this gentleman, agreed on 3 of 5, but not the engine mounts or t-stat. He did his own checks and found the t-stat was functioning fine and the mounts didn't need replacement. He said for $400-$500 I wouldn't notice any difference. I'm going to do them this summer anyway because I've read enough that at 117k, they probably will make a difference. Anyway, the cat had to be done and so did the gaskets. It cost me over $1,700, but those were issues that needed to be addressed. The noise is still there. I like the PCV, which I didn't mention to my mechanic because I think he had enough of my theories for one day, but when I go back for my oil change and once my *** stops hurting from this current work, I'm going to ask him because his theory is that it's something in the engine. He mentioned some kind of pin, but I don't remember. I'm still feeling like the PCV is the culprit because it came out of nowhere initially. If it was something in the engine, I think it would have occurred over time. Thanks for the input on the PCV!

DKoehne12

It is super easy and only about $20. I didn't do it yet. I glued it together and zip tied it and it has been doing perfect since. I just need to pick one up. You can do it yourself. My noise came out of no where also. If you just bump it the membrane inside comes apart and then you have that problem. I would definitely say it is your PCV.

wmerchle

Did your weird sound, sound like this?

The link below is to a recording I made of my mystery sound... Its inside the the google drive folder. You can hear it distinctly at seconds 2, 7 and 11. It is also way more noticeable if you are wearing headphones.

https://drive.google.com/file/d/0B1y...ew?usp=sharing