Q7 Stalling at Idle: Tank Vent Valve Troubleshooting Tips

Had similar symptoms with my A6 3.0 TFSI from 2012. The engine light came on and idle was rough, especially after refueling. Diagnosis revealed multiple issues with the EVAP system, specifically clogged hoses and a faulty pressure sensor near the fuel tank. The ventilation valve was actually fine, the main culprit was debris buildup in the vapor lines. The emission system was struggling to manage fuel vapor properly, causing the engine management to get confused. This made the engine run rich and stall at idle. The repair involved cleaning the entire EVAP system and replacing two damaged hoses. This was not a quick fix, the entire fuel tank had to be dropped to access some components. While not immediately dangerous to drive with, ignoring these symptoms can lead to increased fuel consumption and potential damage to other engine components. The root cause in my case was using low-quality fuel over time. Would strongly recommend getting a proper diagnostic scan first, as replacing the ventilation valve alone might not solve the underlying issue if your problem is similar to what I experienced.

Thanks for sharing your experience. I am dealing with very similar issues, including the rough idle and engine light. Mine also shows the same symptoms after filling up the gas tank, good to know about the EVAP system being the potential culprit. How much did the repair cost in total? Also, has anything else come up since the fix? Wondering if cleaning the system and replacing those hoses was a permanent solution or if you had to deal with related problems later.

The repair bill came to 175 Euro for cleaning the system and replacing the clogged hoses, which turned out to be a good investment. Since getting the tank ventilation issue fixed professionally, the check engine light has stayed off and the idle problems have completely disappeared. The emission system is now working exactly as it should. It has been a permanent solution, no related problems in the months since the repair. The key was getting a thorough diagnosis that identified all the affected components in the EVAP system rather than just replacing parts out of nowhere. The engine runs smoothly now, especially after refueling when it used to struggle the most. The purge valve ended up being fine, as the main issue was indeed the clogged vapor lines. If you are experiencing the same symptoms, getting the entire system checked would be the smart approach rather than focusing on individual components.

Thanks everyone for your input. I finally got it fixed last week. I took it to a different automotive repair shop that specializes in VAG cars. The mechanic immediately suspected the EVAP system when I described the symptoms. The diagnostic scan showed multiple fault codes related to the tank ventilation system. They found that the pressure sensor was faulty and several vapor lines were severely clogged. Total repair cost was 320 Euro, more expensive than expected but worth every cent. They cleaned the entire emission system, replaced the bad sensor and two damaged hoses. The car runs perfectly now, no more stalling, no check engine light, and the idle is smooth even after filling up. Much better experience than with my previous mechanic who just wanted to replace unusual parts without proper diagnosis. Lesson learned: finding a shop that actually takes time to diagnose the real problem rather than just throwing parts at it makes all the difference.