Audi A6 Exhaust Leak Causes Rough Engine & Cabin Smell

I had a very similar issue with my 2006 Audi A4 2.0T last year. I have some basic experience working on cars but leave complex issues to professionals. The engine light came on and I noticed poor performance along with a strong exhaust smell. My initial thought was just an exhaust pipe leak, but the workshop did a proper diagnostic scan that revealed a faulty lambda sensor. This was causing incorrect fuel mixture readings and affecting the catalytic converter performance. The total repair cost was 375 Euro, which included diagnostics, parts, and labor. After replacement, the engine ran smoothly again and the exhaust smell disappeared completely. Given your symptoms, it sounds very similar, but there are a few things worth checking first. Could you share: Current mileage on your A6, Any recent repairs or maintenance, Whether you notice the smell more during acceleration or idle, If the engine light is solid or flashing, Any noticeable changes in fuel consumption This information would help determine if you are dealing with the same issue or possibly something else in the exhaust system.

Thanks for your detailed response. The current mileage is 96522 KM and the last service was done 2 months ago, just a standard oil change and inspection. Had a mechanic check it today and it turned out to be a combination of issues. The exhaust pipe leak was real, but the main problem was indeed a failing catalytic converter. The EGR valve also showed signs of carbon buildup which contributed to the rough running. They did a diagnostic scan which showed multiple codes related to the exhaust system and emissions. They suggest a complete repair including the catalytic converter, fixing the exhaust leak, and cleaning the EGR valve. Quoted 850 Euro for everything. Planning to get it done next week since I dont want to risk more damage to the engine or face emissions test issues.

Good to hear you got it checked out. Your issues are almost identical to what I experienced with my A4 last year, though mine turned out more extensive as it progressed. The catalytic converter failure makes perfect sense with those symptoms. When mine eventually failed completely, it triggered multiple exhaust-related codes and the engine light stayed on constantly. The bad oxygen sensor readings combined with the exhaust leak created a snowball effect, damaging the catalytic converter over time. 850 Euro for the complete repair package is actually reasonable considering the parts involved. When my cat went bad, I initially tried just fixing the exhaust leak, but ended up paying more in the long run by not addressing all related issues at once. The EGR cleaning should help prevent future problems too. Quick tip: After the repairs, make sure they do a complete system reset and check if the DEF fluid level is correct. This helps ensure all emissions systems work properly together. Also worth having them check the remaining oxygen sensors while everything is apart, as they often wear out in pairs. Taking care of it now is definitely the right call before it leads to more expensive problems.

Thanks for the insights. You're right about addressing everything at once, it does make more sense financially. Just got the car back from the shop today. They replaced the catalytic converter, fixed the exhaust leak at the manifold, and cleaned the EGR valve as planned. The oxygen sensor readings are now normal and the engine light is off. Total came to 875 Euro which was slightly above the quote but worth it since they also replaced a cracked vacuum line they found during the repair. The difference in performance is remarkable. No more exhaust smell in the cabin, engine runs smooth, and fuel consumption has already improved. The mechanic said the old catalytic converter was completely clogged, which explains the rough running and poor performance. For anyone searching with similar issues, if you have an exhaust leak combined with engine performance problems, get it checked right away. The diagnostic scan showed exactly what was wrong and saved time guessing. The particulate filter was also checked but thankfully was still in good condition.