RS4 Stalling: EVAP System Causing Idle Problems

I faced a very similar issue with my 2006 RS6. As someone with moderate DIY repair experience, the symptoms you describe match exactly what I encountered. The check engine light kept triggering due to a fault in the emission system. After diagnosis, the problem was traced to clogged hoses in the tank ventilation system, which affected the purge valve operation. The pressure sensor readings were all over the place. My repair bill came to 175 Euro, covering the cleaning of the ventilation hoses and a system check. The mechanic also tested the purge valve, which turned out to be functioning correctly, the clogged hoses were the actual culprit. The repair resolved both the check engine light and the stalling issues completely. The whole job took about 2 hours at the workshop. To provide more specific advice about your situation, could you share: Any specific error codes from the check engine light? Does the stalling happen more frequently after refueling? Have you noticed any problems when filling up the fuel tank? Any unusual fuel tank pressure or vacuum sounds when removing the gas cap?

My last service was at 146000 KM and included new spark plugs and coil packs. You precisely described the symptoms I experienced. My purge valve was sticking open causing the stalling at idle. The tank ventilation issues also triggered erratic fuel gauge readings. The check engine light errors pointed to evap system problems. After cleaning the system and replacing the purge valve for 220 Euro, all issues cleared up. Been running smoothly for the past 3 weeks now.

Thanks for sharing your repair outcome. It matches my experience exactly, these RS models seem prone to EVAP system issues around that mileage. Like yours, my car had similar symptoms with the erratic fuel gauge and check engine light warnings tied to the purge valve. Good call on replacing the purge valve completely rather than just cleaning. While my initial fix with just cleaning the hoses worked for a few months, I eventually had to replace the purge valve too when the problems returned. Since the full replacement, no more stalling or check engine warnings for over 8 months now. The total repair cost seems standard, I initially saved money with just the cleaning but ended up paying more in the long run having to do it twice. For anyone else reading this thread, if you get EVAP system codes along with stalling, checking both the ventilation hoses and purge valve is crucial for a complete fix. Have you noticed any improvement in fuel efficiency since the repair? My gas mileage got noticeably better once the system was working properly again.

Thanks for the detailed input. Just wanted to close the loop on my RS4 issues. After the purge valve replacement and EVAP system cleaning, my fuel efficiency improved by about 15%. The stalling completely stopped and the check engine light hasnt returned. The pressure sensor readings are now stable and the tank ventilation system works as it should. The 220 Euro repair cost was worth every cent considering the problems it fixed. My mechanic mentioned these issues are quite common after 140000 KM, so regular maintenance of the fuel tank components is important. The diagnostic process was straightforward, the error codes pointed directly to the EVAP system, and the symptoms matched perfectly with a faulty purge valve. For others dealing with similar problems, make sure to have both the ventilation system and purge valve checked. Just cleaning the system might work temporarily, but replacing worn components provides a more permanent solution.