Audi S8 Stalling: Tank Ventilation System Failure Alert

As someone with moderate car repair experience, I had a very similar issue with my 2015 Audi S7 last year. The engine light came on and the car showed identical symptoms, rough idle but smooth operation at higher RPMs. After checking the EVAP system, my mechanic found several clogged hoses affecting the tank ventilation system. The issue turned out to be debris accumulation in the ventilation lines connecting to the pressure sensor. The entire EVAP system was compromised due to these blockages. The repair involved cleaning the hoses and replacing a few that were too damaged. Total cost was 175 Euro including diagnostic work. The automotive repair process took about 4 hours, but the car has run perfectly since then. No more stalling issues and the engine light cleared up immediately after the fix. To better assist with your specific case, could you share: Have you scanned for error codes? Does the stalling happen more frequently after refueling? How long has the engine light been on? Any recent changes in fuel type or brand? These details would help determine if your S8 is experiencing the same EVAP system issues I encountered.

Thanks for sharing your experience. My Audi has 50929 KM and last service was done 2 months ago. I actually got the codes read yesterday, P0441 and P0456, both pointing to the EVAP system. The stalling happens regardless of fuel level, but gets worse right after filling up the fuel tank. The check engine light has been on for about a week now. The pressure sensor readings seem erratic according to my OBD scanner. Before booking a repair shop appointment, I want to understand if cleaning the system might work or if I should expect to replace components. The ventilation issues you described sound very similar to what I am experiencing. I was hoping someone had found a reliable fix without having to replace the entire EVAP assembly since the repair costs for these tank ventilation components can get quite high.

Based on those error codes and symptoms, it definitely sounds like we have the same EVAP system issue. After my repair last year, I learned quite a bit about these systems. The P0441 and P0456 codes together strongly suggest a leak in the emission system, similar to what caused my stalling problems. Since your symptoms worsen after refueling, this matches the clogged ventilation pattern I experienced with my Audi. The good news is that a full EVAP assembly replacement probably isnt needed. In my case, cleaning the ventilation lines and replacing just two damaged hoses fixed the issue. The automotive repair shop initially quoted me for a complete system replacement at 890 Euro, but the actual fix was much cheaper at 175 Euro. A reliable fix should include: Thorough cleaning of all EVAP system hoses, Pressure testing to locate any small leaks, Inspection of the purge valve operation, Verification of fuel tank pressure sensor readings After these steps, my idle problems completely disappeared and the check engine light stayed off. The whole repair process was straightforward once the actual problem was identified. Since your vehicle shows identical symptoms, I would recommend starting with the cleaning service before considering more expensive component replacements.

Thanks for the detailed feedback. I scanned the engine codes again today and noticed something interesting, P0440 has now appeared alongside the other codes, which seems to confirm the EVAP system diagnosis. This definitely aligns with your experience. I checked prices at several repair shops and the quotes range from 150 Euro to 950 Euro, with the higher ones pushing for complete system replacement. Given your success with just cleaning and minimal parts replacement, I will opt for a shop willing to try the less invasive approach first. The check engine light is still on but I have an appointment scheduled for next week. They will start by inspecting and cleaning the tank ventilation components, then pressure test the system before deciding if any parts need replacement. Makes more sense than jumping straight to replacing expensive components. Will update once the repair is done. Really helpful to hear from someone who resolved similar symptoms without a complete EVAP system overhaul. Hoping my fuel tank ventilation issues can be fixed with a thorough cleaning like yours was.