SQ8 NOx Catalyst Failure Causing Exhaust Leaks

Recently dealt with a similar exhaust leak issue on my S7 (2018, gasoline). The symptoms matched exactly, check engine light, distinctive exhaust noise, and catalyst-related codes. The root cause was a failed seal between the catalytic converter and the exhaust manifold, allowing exhaust gases to escape. This affected both fuel efficiency and emissions control, particularly the NOx catalyst system. The leak was causing the engine to run rich to compensate, which put additional stress on the catalytic converter. The repair required removing the entire exhaust manifold to access and replace the failed gasket and damaged mounting hardware. While the system was apart, the mechanic found slight damage to the catalytic converter heat shield, which also needed attention. This is definitely a serious issue that needs prompt attention. Exhaust leaks can allow harmful nitrogen oxides and other emissions to enter the cabin, impacting air quality. They also prevent the emissions control system from working properly. The problem typically worsens over time and can lead to more extensive damage if not addressed. Would strongly recommend having it checked by an authorized dealer given the complexity of modern exhaust systems, especially on performance models.

Thanks for sharing your S7 experience. That exhaust system issue sounds very similar to what I am seeing with my SQ8. Really helpful to know about the potential root cause with the failed seal and how it impacts the NOx catalyst system. Just finished scheduling an appointment for car diagnostics at a specialist shop. Before I go in, would you mind sharing what the total repair cost was in your case? Also curious if youve had any other exhaust or emissions-related problems since getting it fixed? Want to make sure I budget appropriately and know what to watch out for to maintain proper fuel efficiency going forward.

Happy to report back on my S7 repair experience. The fix was successful and I havent encountered any exhaust system or emissions problems since then. The NOx storage catalyst aging issue was completely resolved after the repair. The total cost came to 265 Euro for fixing the exhaust leak, which included replacing the failed seal and addressing the mounting hardware issues. This was actually less than I initially expected for automotive repair work of this nature. The repair shop confirmed that catching it early prevented additional damage to the nitrogen oxides control components. The fuel efficiency returned to normal once the exhaust system was properly sealed again. One tip, make sure they thoroughly check all the connecting points while the system is exposed. In my case, they identified and prevented potential future issues by inspecting the entire NOx catalyst assembly during the repair. Going to a specialist shop was definitely the right choice for addressing this type of emissions system problem. Their diagnostic equipment could precisely pinpoint where the exhaust gases were escaping.

I wanted to update everyone on how my SQ8 repair went. After getting the helpful feedback here, I took it to a specialized automotive repair shop for proper car diagnostics. Turns out the issue was exactly what was described, a failed seal between the catalytic converter and exhaust manifold. The leak was affecting the nitrogen oxides control system and causing the check engine light. The repair cost came to 380 Euro total, which included replacing the damaged seal, some mounting hardware, and a full emissions system inspection. The shop used specialized equipment to verify the exhaust gases were now properly contained and the air quality sensors were functioning correctly. The car runs perfectly now, no more strange sounds and the check engine light is off. Fuel efficiency has notably improved since the repair. Really glad I addressed this promptly before it could cause more extensive damage to the NOx storage catalyst. For anyone facing similar issues, would definitely recommend getting it checked by specialists who understand modern emissions systems. The diagnostic tools they use make a huge difference in pinpointing exhaust leaks accurately.