RS6 Power Loss & Smoke Points to PCV Valve Failure

Had the exact same symptoms on my RS4 (2016) with the same 4.0L engine. The PCV system was completely clogged, causing excessive crankcase pressure. Main signs were blue-gray smoke from exhaust, rough idle, and significant power loss especially during acceleration. The ventilation issue was causing oil to get pushed past the seals into combustion chambers. The clog also made the engine run rich due to unmetered air entering the intake. This explained the check engine light. Required complete PCV valve replacement along with all associated hoses and seals. The original parts showed heavy oil residue buildup and cracking in rubber components. This was a serious repair that needed immediate attention to prevent internal engine damage. The leak symptoms got much worse in cold weather when the PCV system was most stressed. If left unfixed, it can lead to oil consumption issues and potential turbocharger damage. After replacement, performance returned to normal, smoke disappeared completely, and engine running smoothly again. Regular PCV maintenance is now part of service schedule to prevent recurrence.

Thanks for the detailed response about your PCV valve experience. The symptoms match exactly what I am seeing with my RS6. Good to know the fix worked well for you. Quick question, do you remember roughly how much the complete repair cost with parts and labor? Also, has everything stayed problem-free since the PCV system replacement or have you noticed any other emissions or smoke issues popping up? The cold weather comment is especially relevant since my smoke and power issues do seem worse on cold starts. Just trying to budget properly and ensure I address everything while its being serviced.

Just had the complete repair done last week actually. Total bill came to 360 Euro for the full PCV valve system replacement, including all related hoses and seals. The crankcase ventilation system is now working perfectly, no more smoke, power loss, or emissions problems at all. Running much smoother overall since the repair. Cold starts are back to normal with no smoke or rough idle. The engine ventilation is doing its job properly now, maintaining correct pressure in the crankcase. Worth every cent to prevent more serious engine issues down the line. No new problems have appeared since the fix. The leak symptoms are completely gone and performance is back to factory spec. Would definitely recommend getting it done soon before the ventilation issues cause any additional engine damage. The longer these valve problems go unaddressed, the more expensive repairs can get.

Thanks for the input. Wanted to give a quick update on how things turned out with my RS6. Finally got the repair done at a specialized performance shop. The maintenance inspection confirmed the crankcase ventilation system was the culprit. Multiple components were completely clogged with oil residue. The valve itself was damaged beyond repair. Total cost ran about 420 Euro for parts and labor. A bit more than expected but the shop did a thorough job replacing the entire PCV system and all connected hoses. They also cleaned out the intake manifold while they were in there. Car runs like new now. No more smoke from the exhaust, power is fully restored, and check engine light is gone. Cold starts are smooth again with no issues. Really glad I caught this before it caused more serious engine problems. Great call on diagnosing this as a ventilation system issue. The symptoms matched perfectly and getting it fixed properly was definitely the right move.