A4 NOx Catalyst Leak Causing Check Engine Warning

Having experienced similar issues with my 1997 Audi A6 2.5 TDI, I can relate to your exhaust system concerns. The symptoms you describe strongly suggest a potential NOx catalyst failure, which was exactly what happened in my case. During car diagnostics, they found the exhaust leak was actually coming from a cracked connection between the NOx catalyst and the downpipe. The automotive repair revealed multiple issues: the NOx catalyst had internal damage, and the mounting brackets were severely corroded. The emissions system repair turned out to be quite serious, as a failing NOx catalyst can lead to increased fuel consumption and potential engine damage if left unattended. The repair required replacing both the catalyst and associated mounting hardware. Key points to discuss with your mechanic: Request a complete emissions system inspection, Ask them to check all mounting brackets and connections, Have them verify if the NOx sensor is functioning correctly, Get a written report of all diagnostic findings For finding a reliable shop, look for those specifically certified in Audi emissions system repairs and who have proper diagnostic equipment for VAG vehicles.

Thanks for sharing your experience. These emissions system issues can be tricky. I also faced NOx catalyst problems with my A4 last year. Before committing to replacing parts, the shop did thorough car diagnostics which helped identify the exact problem areas. Just curious, do you remember what the total repair cost came to for your A6? Also wondering if youve had any other emission-related problems since the fix? The fuel efficiency on these older Audis can really suffer when the catalyst starts failing.

Thanks for asking about the repair costs. After seeing the mechanic, they resolved the NOx storage catalyst aging issue completely. The repair focused on fixing the exhaust leak which was impacting air quality and emissions. Total cost came to 265 Euro for parts and labor. The car diagnostics showed the connection between the NOx catalyst and exhaust pipe needed attention. Since the repair, the catalytic converter has been working perfectly with no other emission-related problems. Fuel consumption returned to normal levels and the engine runs much cleaner now. The thorough inspection really paid off, catching these NOx emissions issues early prevented more expensive problems down the line. The exhaust system has been leak-free for months now, and regular checks help maintain optimal performance.

I finally got my A4 checked out at the repair shop. Like you mentioned, proper car diagnostics made all the difference. The mechanic found that the NOx storage catalyst was indeed failing, causing those exhaust leaks and poor fuel efficiency. The total repair came to 780 Euro, which included replacing the catalyst and fixing some corroded mounting brackets in the exhaust system. The shop specializes in emissions system repairs, and they really knew what they were doing. Been driving for about two weeks since the fix. The check engine light is gone, and the air quality around the exhaust is noticeably better. No more worrying smoke or strange smells. The engine feels more responsive too, and fuel consumption has improved significantly. Really glad I addressed this early, the mechanic mentioned these issues can lead to much costlier repairs if left unchecked. Planning to keep up with regular emissions system maintenance from now on.