Audi S4 Stalling: EVAP System Causing Idle Problems

Had exactly this issue on my 2003 Audi S3 last year, and with some basic car repair experience, I initially thought it was just the gas cap not sealing properly. The check engine light kept turning on, and I noticed similar stalling issues, especially after the engine warmed up. After checking the basic stuff like the gas cap and pressure sensor connections, I took it to a workshop. Turned out the main issue was clogged hoses in the EVAP system, which was causing the purge valve to malfunction. The buildup was preventing proper vapor flow, triggering system errors. The total repair came to 175 Euro, including cleaning of the system and a preventive replacement of some worn hoses. Before jumping straight to replacing the tank ventilation valve, I would suggest having the entire EVAP system checked for blockages. Could save you from replacing parts unnecessarily. To help diagnose this better, could you share: Are you getting any specific error codes? Does the stalling happen more after refueling? Have you noticed any fuel smell? When was the last time your purge valve was checked? These details would help determine if your issue matches what I experienced with my Audi.

I had my car serviced last month at 44910 KM and really appreciate the detailed response. Your experience seems very similar to what I am experiencing with my emission system issues. The engine light comes on right after refueling and I do notice a faint fuel smell sometimes. After reading your reply, I will have the EVAP system hoses checked first before replacing the tank ventilation valve. I was too focused on just swapping parts without considering a possible blockage could be causing these symptoms. The stalling is definitely worse after filling up the fuel tank and I get error code P0441 consistently. I have not had the purge valve checked yet, so that will be my first step based on your suggestion.

Thanks for those additional details, the P0441 code and symptoms after refueling match exactly what I experienced with my Audi. After having gone through this repair, Id strongly recommend getting the purge valve checked first since its often the root cause when stalling occurs post-refueling. In my case, the clogged hoses were preventing the purge valve from functioning correctly, causing the check engine light to illuminate repeatedly. A quick diagnostic tip from my experience: try listening near the engine bay for a clicking sound when starting the car. A properly working purge valve makes an audible click. If you dont hear it, theres a good chance the valve is stuck. The fuel smell you mentioned is another typical sign of EVAP system issues. Just like in my repair case, it could indicate that fuel vapors arent being properly contained due to either blocked hoses or a malfunctioning tank ventilation system. The repair costs should be similar to what I paid (175 Euro), assuming its the same issue. Make sure whoever does the work checks the entire vapor path from the gas cap to the purge valve, as partial repairs often lead to recurring problems. Have you noticed if the stalling gets worse on particularly hot days? This was another symptom I experienced before getting it fixed.

Thanks everyone, this feedback has been really helpful for my S4 problems. After considering the responses and symptoms, I am going to take the following steps: 1. Get the purge valve checked and listen for that clicking sound when starting 2. Have the entire EVAP system inspected for blocked hoses, especially since the stalling does get worse in warm weather 3. Get the emission system vapor path tested from gas cap to purge valve The P0441 code, fuel smell, and stalling after filling the fuel tank really do point to an EVAP system issue rather than just a bad tank ventilation valve like I first thought. Will probably save money by having everything checked properly instead of just replacing parts. At 175 Euro for a full system inspection and repair, its worth doing it right. Better than continuing to deal with the engine stalling and check engine light coming on. Will update once I get it looked at.