Diesel Sound, Rough Idle In Park Only, Hissing Sound, Clunk
 

Few questions for you professionals - I'm at my wits end.

Ok, first... its a B6 2005 Audi A4 3.0 Quattro 5-speed Tiptronic Transmission - roughly 66,000 miles. Purchased it this March... since then I've done the timing belt, serp tensioner, water pump, plugs, 4 rotors, 4 pads, oil change (0w40 mobil 1), fuel filter, model specific K&N intake filter (oem box), coolant, brake fluid, transmission fluid/filter/gaskets, front and rear diff gear oil, rear main seal... and I think that's about it.

Absolutely zero fault codes. None.

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Anyway I'm having a few issues and hope you can steer me in the right direction.

1.) When decelerating at low speed (i.e. let off the gas in a parking lot or drive through) the engine sounds like a diesel. tick tick tick tick tick tick. When I give it gas, the tick goes faster until about 1500-2000rpm and then it goes away. When I slow down, the tick comes back and slows with the RPM.

2.) When the car is in park, once it warms up and the RPM goes back down to "normal", the car shakes. Not like an earthquake, but certainly not smooth and very noticeable vs when parked in drive (at a stop light for example). Once I put it in any gear (R, D, TIP, S) it goes away. Granted, in "gear" the idle rpm is higher, but this seems strange.

3.) I just noticed recently (now that it's colder out) that I can hear a hiss/whistle sound from the center/right of the front of my car anytime I accelerate. Most pronounced around 2800-3000RPM, but if I let off, on, off, on it will still do it. Sounds like a turbo or quiet blow off valve almost, and my N/A V6 does not have either. My PCV was just delivered today, going to give that a shot. I didn't order hoses though, so if it's a leak then I'll have to get them. Hoping I can snake it under the intake manifold without removing 1/2 the engine.

4.) Most noticeable after parking, when I go from park to drive, or park/reverse/drive and take off (go forward) the front of my car makes a CLUNK sound - I can feel it in the pedals. Once I'm moving, it doesn't happen again. Was thinking it may be the brake pads, or control arms... but the pads don't show any wear from sliding around (at least externally - haven't taken them apart), and I'm not sure how to test the control arms without just replacing them.

Any ideas, tips, etc. would be greatly appreciated.

Thank you so much!!!

got a decent video of it once. Between 3-4 seconds in. Sorry it was dark.

https://youtu.be/igCC7MNvv9w


Here's the clunk around 1-2 seconds in

https://youtu.be/DTEPGp6XiPo

Changed the PCV. Significant improvement in my park idle. Very significant.

That said, what kind of suction is allowed? I can take the oil fill cap off fine (some said it has to be next to impossible) , but when I put my hand over the hole there is certainly a good amount of suction. How much is too much or too little if any? Would this warrant new vac hoses?

Thank you!
https://cimg1.ibsrv.net/gimg/www.aud...4714e283a0.jpg

https://cimg2.ibsrv.net/gimg/www.aud...a473daf704.jpg

Pcv dramatically improved idle. Honestly it's probably fixed. However... when I take the oil cap off (which I can still do fairly easily) there is still a good amount of suction. If I cover it with my hand it certainly has suction.

How much is too much? Is there a minimum? Or do I have a leak in a hose somewhere?

Thanks!

You mean the oil cap, right? If you take it off and set it back on the hole, it should dance around.

the diesel sound is probably the cam chain tensioner.
These are hydraulic and have guides on them them that wear.
I had the same on my sons, he turned up one day and I would have sworn it was a diesel by the sound. He had it at the dealer mechanic who told him 'they all sound like that'.

Anyway I fitted a new chain & tensioner, its all quiet now. (so they don't all sound like that!).

Lots of people have problems with aftermarket tensioners, and a genuine one is $$$. It seems like most people find that the pads are worn, and replacing just the pads fixes the issue.

Yes oil cap! Sorry... dont know why I said that lol.

Local Indy shop found a leak between the throttle body and the engine. Going to have them replace the gasket, clean the throttle body a bit, and replace the vacuum lines with new 3.5mm lines while they're there. Hopefully that explains the poor performance and the diesel sound. If it doesn't - I guess the chain tensioner is next on the list. Sigh...

Thanks everyone!

Thanks for the info everyone! And for the corrections - my first german car so obviously I need to be more precise in my verbiage vs my chevrolet LOL.

Took it to the indy shop and they did a VAG scan - the throttle body adaptation will not work. The error code (which I didn't think to ask for since they are friends of mine) will not clear. He said most likely the throttle body is dirty and needs to be cleaned, new o-rings, and then do the adaptation. I also picked up the breather hose for under the intake manifold since he'll be right there anyway. Also got new vacuum lines, new check valves, and a few misc clips that I noticed were replaced with zip ties by the PO. Hopefully that does it.

With that said, question... would a dirty unadjusted throttle body make the diesel sound at low rpm when on and off the gas in a parking lot? I'd imagine it's dumping fuel to overcompensate for how lean it is and essentially stalling the engine which is restarted by me moving in gear. Sounds plausible - and would be WAY better than lifters/cams/etc.

I'm waiting on parts, should get them in and get the job done early next week. Will keep you posted.

Couple more videos if this helps too.

Clunk:
Diesel sound: