Audi TT Engine Stalling Points to Faulty Tank Vent

As an A4 2.0T owner from 2008, I encountered nearly identical symptoms. The check engine light repeatedly activated due to an EVAP system malfunction. The main issue was indeed related to tank ventilation, specifically a clogged purge valve and deteriorated vapor lines. The symptoms match perfectly: stalling at idle and recurring engine light issues are classic signs of a compromised EVAP system. The purge valve gets blocked with carbon deposits over time, preventing proper fuel tank ventilation. In my case, the automotive repair revealed multiple problems: 1. The purge valve was completely clogged 2. Two vapor lines had cracked from age 3. The charcoal canister was saturated This turned out to be a serious issue requiring immediate attention, as it affects both emissions and fuel system pressure. Ignoring it could lead to fuel pump damage and poor engine performance. The repair involved replacing the purge valve assembly and all connected hoses. Worth checking these components before replacing the entire EVAP system. A qualified technician can perform a smoke test to pinpoint exact leak locations in the system.

Thanks for the detailed response about your experience with the A4. Very interested to hear about your similar EVAP system issues. I just got my TT back from the shop last week with a new purge valve and vapor lines. While the check engine light has stayed off since the repair, I notice it still occasionally has a slight hesitation at idle. Wonder if this will settle over time. Mind sharing how much you ended up paying for your fix? Also curious if youve had any recurring tank ventilation problems since the repair was completed. My gas cap seems a bit loose too, so might have that checked while Im at it.

Really glad to follow up on this. After my previous issues with the A4, I had the EVAP system fully repaired and the tank ventilation valve malfunction was completely resolved. The repair cost came to 175 Euro, mainly for fixing the clogged hoses and labor. The slight hesitation you mention should improve within a few hundred kilometers as the system fully adapts. Had the same temporary quirk after my repair but it smoothed out. Haven't experienced any recurring problems in the fuel tank system since getting it fixed. Definitely get that gas cap checked, a loose seal can trigger the check engine light and cause similar symptoms. Most parts stores can test if its sealing properly. Its a small fix that can prevent bigger EVAP system headaches later. The automotive repair was worth every cent considering how the car runs now. Just keep monitoring for any unusual idle behavior, but based on my experience, you should be in good shape with the new components installed.

Thanks for the advice. Finally got everything sorted out last week after taking it to a different mechanic for a second opinion. The emission system diagnosis showed multiple issues, turns out the pressure sensor was faulty alongside the purge valve problems. Total repair came to 320 Euro including parts and labor. The idle is now completely smooth and the check engine light has stayed off. The mechanic also replaced my gas cap as a precaution since it wasnt sealing properly. They did a thorough smoke test after the repair to confirm the tank ventilation system was working correctly. Really glad I didnt wait longer to get it fixed. The car runs so much better now and fuel economy has improved too. The repair shop did a great job explaining everything and showing me the old parts. Much better experience than my first mechanic visit where they missed half the issues.