Q3 Stalling at Idle: EVAP System Pressure Issues

Had the exact same symptoms on my 2015 Q2. As someone with some hands-on experience working on cars, these symptoms immediately pointed to an EVAP system issue. The check engine light came on first, followed by the stalling problems. The pressure sensor readings were inconsistent, which led to a system failure warning. After diagnostic testing, the workshop found that the activated charcoal filter was completely clogged, blocking proper air flow through the purge valve. The repair involved: Complete system diagnosis, Replacement of the activated charcoal filter, Clearing fault codes, Testing the purge valve operation Total cost was 275 Euro and the issue never came back. The car runs perfectly now with stable idle. To help diagnose your case more accurately, could you share: Current mileage, Any other warning lights, Whether the stalling happens more frequently after refueling, If you notice any fuel smell, The specific fault codes if you have them These details would help determine if your issue is identical to what I experienced.

Thanks for sharing your experience. Just had my last service at 80466 KM and they didnt spot anything unusual with the emission control systems. The stalling happens more frequently after refueling and there is a faint fuel smell. The fault code reader shows P0456 which points to a small EVAP leak. The air flow seems normal when driving but the system failure occurs mainly during idle. My mechanic suspects either a faulty purge valve or deteriorated fuel tank vent lines, but wants to run more tests to be certain. The fuel efficiency has also dropped slightly in the past month. Would be helpful to know if your mechanic ran any smoke tests before replacing the charcoal filter?

Thanks for the additional details. Your symptoms are even more similar to what I experienced than I initially thought. The P0456 code is exactly what I had, along with that characteristic fuel smell and post-refueling stalling. My mechanic did perform a smoke test before replacing the charcoal filter. The test revealed minor leaks in the EVAP system around the purge valve area, but the main issue was definitely the clogged charcoal filter restricting proper air flow. The fuel efficiency drop you mentioned was also present in my case. I noticed about a 10% decrease before getting it fixed. The leak detection test showed the system wasnt maintaining proper pressure, which explained both the efficiency loss and the fuel smell. Important note: if youre experiencing the same fuel efficiency drop with similar symptoms, Id recommend not delaying the repair. The clogged filter puts extra stress on the entire fuel tank ventilation system, which could lead to more expensive repairs if left unchecked. Since your mileage is similar to what mine was when the issue occurred (I was at about 85000 KM), its likely the same root cause. The charcoal filter tends to degrade around this mileage point in these models.

Thanks for the input. After reading about your similar experiences, I went ahead and had my mechanic do a complete leak detection test. You were right, the smoke test revealed the charcoal filter was the main culprit, though there was also a small crack in one of the vent lines. Total repair came to 320 Euro including: New charcoal filter, Replacement of the cracked fuel tank vent line, System pressure test, Purge valve inspection, Clearing the check engine light Car runs perfectly now, no more stalling at idle and the fuel efficiency is back to normal. The fuel smell is completely gone too. Really glad I caught this early before it caused more serious issues. For anyone else reading this with similar symptoms, definitely get the smoke test done, it helps pinpoint exactly where the EVAP system is failing. The combination of stalling, check engine light, and that subtle fuel smell seems to be a classic sign of this particular problem.