Do I have a bad PCV or is it something else?

**Broadfield** · 07-18-2023 03:27 PM

2013 S6 with 66k miles

Modifications:

APR Stage 2 ECU tune and APR TCU tune
Milltek Catless downpipes and Milltek non-resonated exhaust
Unknown intakes... were on the car when I bought it
Oil screen issue was performed by Audi about 2 years ago... I think right before they issued the recall.

Symptoms over the course of a few weeks or so.

First noticed the vehicle with a very slight vibration at idle, but didn't do it all of the time.
Slowly it became more common and more vibration.
Then became more like a car with a lopey cam, but didn't do it all of the time.
I then started noticing that the RPM needle would dance a little bit during idle.
Every once in a while, when pulling away from a stop, the car would slightly hesitate.
At this point I replaced the plugs. That didn't help.
It does the hesitation thing pretty much every time when pulling away from a stop now.
It now has the lopey cam feel virtually all of the time at idle. Getting to the point that I'm afraid the vehicle might die when sitting at a stop.
If I pull the oil cap, while the vehicle is running, it has a ton of vacuum... enough to fight me when pulling the cap.
It does not have the whistle sound that I see/hear in a lot of the "bad PCV" videos. Also referred to in the TSB.
It does make a sound though that I can really only hear with the windows down and coming from the passenger side... very subtle. Does NOT do it at idle. Has been doing this since the beginning of the symptoms... may have been the first symptom actually. It sounds more like a whirring sound that seems to ramp up and down a little and isn't there all of the time. Throttle input doesn't appear to change it... I hear it with typical driving. I don't think it does it under heavy throttle input. Or the exhaust is loud enough that I just can't hear it under heavy throttle input lol.
I have no DTCs... scanned with OBD11 or my Snap-On scanner etc.
Has been using more oil than what is normal

Are there any other tests I can perform before I just assume it's a bad oil separator? I perform all of my own labor, so I don't necessarily mind replacing the oil separator to see if that fixes it. $300 - $400 or so in parts isn't all that bad. But if there's a consensus here that it isn't the oil separator, I won't bother. I have also seen that people say that when the oil separator is bad, the vehicle idles higher, not lower like mine!?! Let me know what you think or if you have any additional questions for me to try and diagnose it better.

Thanks,

Toby