S6 TDI Power Loss & Rough Idle: Fuel Filter Alert

I had a very similar issue with my 2021 Audi A6 TDI. The symptoms you describe match exactly what I experienced, power loss, rough idle, and terrible fuel efficiency. With some experience working on diesel engines, I recognized these as classic fuel system problems. After noticing the issues, I took it to a workshop where they diagnosed a faulty cable connection to the fuel filter heater. The cold start performance was particularly affected. They found the plug connection had corroded, causing intermittent contact issues in the fuel system. The repair was straightforward, they replaced the damaged wiring and connections, costing 95 Euro including labor. The whole job took about an hour, and the difference was immediately noticeable. Power returned to normal, and fuel efficiency improved significantly. To provide more specific advice for your case, could you share: The exact error code stored in the system, Whether the issues are more pronounced during cold start, If you notice any warning lights on the dashboard, How long youve been experiencing these symptoms These details would help determine if youre dealing with the same fuel system issue I encountered.

Thanks for the helpful insights. My Audi S6 has 56252 KM on the odometer since its last service 3 months ago. The error code is P0201 and yes, the cold start performance is particularly bad. The warning light came on about a week ago, around the same time the fuel consumption started increasing. The rough idle is most noticeable during the first few minutes after starting up. I checked the fuel filter area and noticed some moisture around the electrical connections, which matches your experience with corrosion in the fuel system. I think getting the fuel filter heater and wiring checked makes sense as a first step. Good to know the repair was relatively quick and affordable in your case. I will book an appointment and have them look specifically at the fuel line connections.

Your case sounds nearly identical to what I experienced. After seeing you mention the moisture around the connections and the P0201 code, I'm even more convinced it's the same fuel system issue I dealt with. On my A6, the rough idle during cold start got progressively worse over about two weeks before I had it fixed. The fuel consumption increased by nearly 15% during that time. The moisture you spotted is a telltale sign, it was causing corrosion in my fuel filter heater connections, leading to poor electrical contact. One tip from my experience: have them check the entire fuel line while they're at it. My mechanic found some slight wear on other connectors that could have caused problems later. The filter replacement itself is a good preventive measure given your mileage. The P0201 code initially had them looking at injectors, but the real culprit was the compromised fuel filter heater connection affecting the entire fuel system. Engine stalling was the next symptom I started experiencing before getting it fixed, so you're smart to address this early. Would suggest documenting the cold start issues with a video before repair, it helped demonstrate the problem to the workshop in my case.

Thanks everyone for the detailed responses. This has been really helpful in confirming my suspicions about the fuel system issues. After reading about your similar experiences, particularly with the fuel filter heater connections, I feel much more confident about the repair direction. I took a video this morning of the rough idle during cold start as suggested. The moisture around the connections and the P0201 code, combined with my increasing fuel consumption and power loss symptoms, definitely point to the same fuel filter heater problem you all experienced. I have booked an appointment for next week. I will have them check the entire fuel system, including all connections and the filter replacement, given my current mileage. The quoted repair cost is around 120 Euro, which seems reasonable based on your experiences. Will update the forum once the repair is complete in case others run into similar fuel efficiency and rough idle issues with their TDIs. Thanks again for helping me avoid potentially more expensive repairs by addressing this early.