S4 Power Loss & Black Smoke, Diesel Filter Alert

Running an A6 3.0 TDI with similar symptoms led me to discover a severely clogged DPF that was affecting fuel efficiency and performance. The dark smoke and power loss matches exactly what I experienced when the diesel filter reached its capacity limit. The DPF cleaning process became ineffective because the backpressure was too high for proper regeneration cycles. After diagnosis, it showed the filter was about 90% blocked. Manual regeneration attempts failed, indicating the DPF was beyond the serviceable threshold. The resolution required a complete DPF replacement since the contamination level prevented effective cleaning. The work involved removing the entire exhaust section to access and replace the filter assembly. This is a serious issue that will only worsen if left unaddressed, potentially leading to complete engine shutdown. Post-repair, the engine regained full power, smoke disappeared, and fuel consumption returned to normal. These symptoms definitely point to DPF issues, and proper diagnostic equipment is essential for accurate assessment. The repair requires specialized knowledge of diesel particulate filter systems and regeneration protocols. The repair facility should be able to show you the pressure differential readings across the DPF before suggesting any work.

Thanks for sharing that experience. The symptoms you described with your A6 match what I am seeing with my S4. The engine light just started flickering this week, and the sensor fault readings seem to confirm the diesel filter issue. Could you share roughly how much the complete filter replacement cost you? Also curious if you have experienced any similar issues since the repair was done. My local shop quoted 1200 Euro for parts and labor but I want to make sure that is reasonable before proceeding.

After completing the DPF replacement on my A6, I can confirm the total cost came to 1550 Euro, which included both parts and labor. This price aligns with typical vehicle inspection and repair costs for this type of work. Since the diesel filter replacement 8 months ago, fuel efficiency has returned to normal levels and the engine runs perfectly, no more power loss or smoke issues. The DPF cleaning and regeneration cycle now works as intended, with no warning lights or performance problems. The price your shop quoted at 1200 Euro seems reasonable, though slightly lower than what I paid. Just ensure they perform proper diagnostic tests to confirm the DPF is actually the root cause before proceeding with the replacement. A functioning diesel particulate filter is crucial for both performance and emissions, so while the cost may seem high, it is a necessary repair that will prevent more expensive engine damage if left untreated.

After getting that feedback, I finally went ahead with the repair at my local shop this week. The sensor fault readings were spot on, it was indeed a completely clogged DPF causing the issues. The exhaust system had to be partially dismantled to access and replace the filter. The final bill came to 1150 Euro, which included a full vehicle inspection while they had it up on the lift. The mechanic showed me the old filter and it was totally blocked. Since completing the filter replacement yesterday, the engine runs like new again. No more dark smoke, full power restored, and the warning lights are gone. The regeneration process is now working properly according to their diagnostic tests. Really glad I didn't wait any longer as they mentioned the extreme clogging could have led to bigger engine problems. The price ended up being fair for the work involved.