Audi TT Stalling Mystery: Fuel Tank Vent System Suspect

Had a similar situation with an Audi A4 2002 gasoline engine. The symptoms matched exactly, stalling at idle and check engine light, with normal operation at higher RPMs. The issue turned out to be a failing EVAP system, specifically the purge valve and pressure sensor combination. The problem required replacing both components since the defective activated charcoal filter was causing improper fuel tank ventilation. This was a serious issue that needed immediate attention, as it affected both fuel efficiency and emissions control. Ignoring it could have led to complete system failure. The pressure sensor replacement alone did not resolve the problem. The complete fix required: New purge valve, Pressure sensor replacement, EVAP system diagnostic, Charcoal canister inspection After the repairs, the idle problems disappeared completely and the check engine light stayed off. These components typically start failing around 150000-200000km, so the mileage on your TT fits the pattern. Consider getting a full EVAP system diagnostic from a different shop that specializes in VAG vehicles.

Thanks for sharing that A4 experience. My TT had almost identical symptoms last year. Really helped me understand what I was dealing with since the purge valve ended up being the main culprit in my case too. Just wondering, how much did the complete fix cost you in the end? And has everything stayed working properly since the repair? Mine has been running smoothly for about 8 months now, but always good to know what to expect long-term with these emission control systems.

Since my original repair on the A4, everything has worked flawlessly with no recurring EVAP system issues. The leak detection test confirmed the fix was successful, and fuel efficiency actually improved slightly after the repair. The total repair cost came to 275 Euro for replacing the defective activated charcoal filter, which resolved the fuel tank ventilation system leak completely. This was actually less expensive than I initially feared, given the comprehensive diagnosis needed for EVAP system problems. Eight months of trouble-free operation on your TT is a good sign. These repairs typically last several years when done properly. The air flow and emission control systems on these engines are quite reliable once the faulty components are replaced with quality parts. Just keep an eye on your fuel consumption patterns, any sudden changes could indicate early signs of future EVAP system issues.

After getting your feedback, I finally took my TT to a different mechanic who specialized in VAG cars. The complete diagnosis showed exactly what you described, a failing EVAP system. Total repair cost came to 450 Euro including parts and labor, which was more reasonable than I expected. The fix included replacing the purge valve, pressure sensor, and cleaning the whole ventilation system. The check engine light disappeared immediately and the idle problem is completely gone. The car feels much smoother now, especially during cold starts. Most importantly, my fuel consumption has improved noticeably. This whole experience taught me to get a proper diagnosis first instead of paying for unusual checks. The emission control system is actually working perfectly now, and the engine maintains steady idle under all conditions.