Audi A4 Idle Stalling Points to Faulty Vent Valve

Having worked on cars for a few years, I encountered a similar issue with my 2010 Audi A3 2.0 TFSI. The symptoms matched exactly what you describe, check engine light and stalling at idle. The pressure sensor readings were all over the place, and it turned out the tank ventilation system was compromised. The main culprit was clogged hoses in the emission system, which affected the entire fuel tank ventilation. After a thorough inspection, the workshop found debris blocking proper airflow. The repair included cleaning the system and replacing some components, costing 175 Euro in total. Before jumping to conclusions, could you share: Have you checked if the gas cap is properly tightened? Are you getting any specific error codes? Does the problem get worse after refueling? Have you noticed any unusual fuel consumption? This information would help narrow down if your issue matches what I experienced with my A3. These ventilation problems are fairly common in this engine family, but its best to confirm with proper diagnostics.

Thanks for the feedback. I had my last service at 39156 KM. The gas cap was actually one of the first things I checked since its a common EVAP system issue. I did scan for codes and got P0441 and P0455, both pointing to the emission control system. The problem definitely gets worse after refueling, and fuel consumption has increased by about 15% in the last month. The check engine light started flashing more frequently this week. I cleaned around the gas cap seal but that didnt help. Starting to think its definitely the ventilation valve given all these symptoms.

Thanks for providing those details. Those error codes on your A4 definitely align with what I experienced on my A3. The P0441 and P0455 codes point to a compromised EVAP system, and the increased frequency of the check engine light suggests the problem is getting worse. The combination of higher fuel consumption, symptoms worsening after refueling, and the specific codes strongly indicate a faulty purge valve in the tank ventilation system. This matches the progression I saw before getting mine fixed. Since youve already checked the gas cap and seals, the next step would be getting the purge valve and pressure sensor checked. When my A3 had this issue, replacing the purge valve resolved all symptoms, including the fuel consumption increase. My repair included: New purge valve: 85 Euro, Pressure sensor: 65 Euro, Labor: 95 Euro The entire fuel tank ventilation system should be inspected too, as deteriorated hoses can cause similar symptoms. Better to catch any related issues while the system is being serviced. Would you mind checking if you hear a clicking sound from the purge valve when starting the engine? This was another telltale sign in my case.

Thanks for that detailed breakdown. This is exactly the kind of automotive repair guidance I was looking for. I just checked for the clicking sound from the purge valve you mentioned and cannot hear anything when starting up. Combined with those vacuum system issues I noticed and the error codes, I think were looking at the same problem you had. The estimate you provided helps a lot with budgeting for this repair. The total cost around 245 Euro sounds reasonable considering the diagnostic evidence pointing to the emission system components needing replacement. Going to schedule an appointment to get the tank ventilation valve and pressure sensor checked next week since all symptoms match your experience. Will make sure they inspect all the connecting hoses while theyre at it as you suggested. The check engine light and poor idle are getting worse, so best to address it now before it causes additional problems. Really appreciate you walking through your similar experience, helped confirm my initial diagnosis was on the right track.