SQ5 Stalling: Faulty Purge Valve Warning Signs

As someone with moderate expertise working on Audi vehicles, I experienced nearly identical issues with my 2015 S4. The check engine light would illuminate and the engine would stall at idle. Initially, I thought it was just a faulty pressure sensor. After taking it to a workshop, they discovered clogged ventilation hoses connected to the fuel tank system. The blockage was preventing proper fuel tank pressure regulation, which caused the stalling. The complete repair, including diagnostic work and parts replacement, cost 175 Euro. Since your symptoms match what I experienced, it could indeed be related to the purge valve or clogged hoses in the ventilation system. The automotive repair process was straightforward once they identified the root cause. To provide more specific guidance: What diagnostic codes is your check engine light showing? Have you noticed any fuel smell around the car? Does the stalling happen more frequently after refueling? How many miles/kilometers are on your vehicle? These details would help determine if your issue matches what I encountered with my S4.

Thanks for your feedback. Yes, my issue matches exactly what you described. After the last service at 33740 KM, the check engine light started appearing intermittently. The stalling particularly happens right after refueling, and there is a slight fuel smell near the tank area. The EVAP system diagnostic showed a P0456 code, indicating a small evaporative emission system leak. Given the symptoms and your experience, I will have my mechanic focus on checking the tank ventilation components, especially the purge valve and connecting hoses. The quoted repair cost seems reasonable compared to what you paid. Just to be thorough, I will also have them verify the gas cap is sealing properly since that could also trigger similar symptoms.

Thanks for providing those additional details. Having gone through this exact issue with my S4, the P0456 code and fuel smell after refueling strongly confirm my initial suspicion about the tank ventilation system being the culprit. After my repair, I learned that these symptoms often appear in sequence: first the fuel smell, then sporadic check engine lights, and finally the stalling issues. The pressure sensor picks up the small leak, which gradually worsens until it affects engine performance. While the gas cap is worth checking, in my case the main issue was indeed a combination of a failing purge valve and partially blocked ventilation lines. The fuel smell near the tank area is particularly telling, this was exactly what I experienced before the complete repair. The mileage you mentioned (33740 KM) is actually close to when my issues started developing. The repair resolved all symptoms, and I have not experienced any related problems in the 20000 KM since. A quick tip from my experience: once the repair is completed, you might need to drive several cycles before the check engine light clears completely, even after the system is fixed. This is normal as the car needs to run several self-diagnostic cycles.

Thanks everyone for the detailed responses. Just wanted to provide a quick update on my 2013 SQ5 situation. Had my mechanic do the repair yesterday and it confirmed what you all suggested. The purge valve was indeed faulty and there was significant buildup in the fuel tank ventilation lines. Total repair cost came to 190 Euro including parts and labor. They replaced the purge valve, cleaned out the ventilation system, and double checked the pressure sensor connections. The fuel smell is completely gone now and the engine idles perfectly. Even after several test drives, the check engine light has stayed off. Special thanks for the heads up about the diagnostic cycles. My mechanic mentioned the same thing about needing several drive cycles to fully clear the system. Will keep monitoring but so far everything points to a successful fix. Really appreciate all the guidance that helped pinpoint the exact issue.