RS7 Rough Idle Issues Linked to Air Valve Problems

I ran into nearly identical idle problems with my 2013 RS6, and it sounds very similar to what you are experiencing. Let me share my experience as someone with moderate car repair knowledge. The unstable idle and stalling issues were caused by a damaged vacuum hose connection between the fuel pump and the air valve. The throttle body was receiving inconsistent air supply, which caused the manifold pressure to fluctuate. This explained both the check engine light and the rough running conditions. My workshop diagnosed it using pressure testing equipment to locate the exact leak point. The entire repair, including parts and labor, cost 175 Euro. The job took about 2 hours to complete, and the idle problems disappeared completely after the fix. Before proceeding further, could you share: Have you noticed any hissing sounds from the engine bay? Does the rough idle get worse when the engine is warm? Are there any other warning lights besides the check engine light? Have you had any recent work done on the intake system? This information would help determine if your issue matches what I experienced with my RS6 and could save you time and money in diagnosis.

Last service was at 189000 KM and I want to thank you for the detailed response. Looking at your questions: Yes, there is a faint hissing sound near the front of the engine bay, and the idle does get more erratic when warm. No other warning lights are present. The intake system is all original with no modifications or recent work. Your diagnosis about the vacuum leak makes a lot of sense given my symptoms. The way the engine stalls matches perfectly with inconsistent air supply through the throttle body. Getting pressure testing done seems like a smart first step before replacing any parts. At my mileage, these vacuum hoses are probably due for inspection anyway, so this might be the perfect time to address any potential issues in the entire vacuum system.

Based on the additional details you provided about the hissing sound and worsening idle when warm, I am now even more convinced we had the exact same issue. My RS6 was showing identical symptoms at around 175000 KM. The pressure test confirmed what I suspected, the vacuum hoses had deteriorated exactly where they connect to the throttle body. The rubber had become brittle from heat cycles and engine vibration. When my mechanic removed the old hoses, you could actually see tiny stress cracks that were causing the air leaks. A quick tip from my experience: while the system is opened up for the vacuum hose replacement, have them inspect the air valve assembly too. In my case, the seals around the air valve had also started to fail, contributing to the idle problems. Replacing both components at once prevented me from having to do another repair a few months later. The complete job including new vacuum hoses, air valve seals, and labor ended up costing about 250 Euro. The engine has been running perfectly for 40000 KM since the repair with no idle problems or stalling issues. Would recommend getting this addressed soon, as these vacuum leaks tend to get progressively worse and can eventually affect fuel mixture and engine performance.

Thanks for the great information and sharing your experience. Your RS6 case really helps confirm what I was suspecting with my RS7. The matching symptoms, especially the hissing and warmup behavior, make me feel confident about pursuing the vacuum leak diagnosis. Getting both the air valve seals and vacuum hoses checked makes perfect sense from a preventive maintenance perspective. I have scheduled a pressure test for next week. Given the similar mileage when you experienced these issues, I will definitely have them inspect the entire air intake system while they are in there. The 250 Euro repair cost seems reasonable considering the complexity of accessing these components. The fact that your fix has lasted 40000 KM without issues is especially reassuring. I will make sure to update the forum once I get the pressure test results and complete the repairs. Hoping for the same long-term solution you achieved with your throttle body and vacuum system repair.