RS3 Fuel Injection Problems: Multiple System Failures

I faced a comparable issue with my 2015 RS4 about a year ago. Having some experience working on petrol engines, I initially thought it was just a minor sensor problem. The symptoms were nearly identical, poor engine performance, higher fuel consumption, and the same stalling issues. The smoke during acceleration was particularly concerning, as it indicated a fuel system problem. My workshop ran a full system diagnostic and found the root cause was a damaged wiring harness connecting to the fuel injectors. The cable insulation had worn through, causing intermittent connection issues that affected the injection timing and fuel delivery. The repair involved replacing the wiring harness and checking all related connectors, costing 95 Euro including labor. The power and performance were restored immediately after the fix. Fuel consumption returned to normal levels within the next tank. To provide more specific advice about your case, could you share: Current mileage, When these symptoms first appeared, Whether the check engine light is on, Any error codes from previous diagnostics, Recent maintenance history These details would help determine if your issue stems from the same root cause or requires a different approach.

Last service was completed at 82000KM and I am now at 84099KM. The check engine light just appeared and I got error code P0201 which points to cylinder 1 injector circuit malfunction. Thanks for sharing your experience, it sounds quite similar. I will have my workshop check the wiring harness since the fuel system symptoms match what you described. The engine performance issues started gradually over the past few weeks, getting noticeably worse after long highway drives. Hopefully addressing the electrical connections will solve the fuel delivery problems.

Thanks for providing those details. The P0201 code and gradual symptom onset perfectly match what I experienced with my RS4. Since you mention highway drives making it worse, this further confirms my suspicion about the wiring harness, the heat from extended running can expand the damaged insulation and worsen the connection issues. When my workshop did the repair, they actually found the wiring damage was most severe near the hot spots of the engine, particularly around cylinder 1. The heat cycling had accelerated the wear on the insulation. A key maintenance tip after fixing the diesel injection system: have the workshop check the protective sleeve condition around all injector wiring bundles. In my case, they installed additional heat shielding to prevent future issues, which added about 40 Euro to the repair but was worth it for long-term reliability. The good news is that once the wiring was repaired, engine power returned immediately and fuel consumption normalized. The smoke during acceleration completely disappeared since the injection timing was restored to spec. Consider requesting a fuel injector cleaner service while they have everything apart, its relatively inexpensive preventive maintenance that can help avoid future injection system problems.

The error code P0201 matches exactly what I found in my service documentation, and your description of worsening symptoms after highway drives makes a lot of sense now. At 84099KM, these wiring issues are not uncommon in the fuel system, especially considering the high performance nature of the RS3 engine. Based on the similarities to your case, I will definitely have my workshop perform a complete wiring harness inspection, focusing on cylinder 1 where the error code is pointing. The air and fuel system symptoms match too closely to ignore the electrical connection possibility. I appreciate the tip about adding extra heat shielding, will request this preventive measure since I do frequent highway driving where engine temperatures can affect system performance. Will also take your advice on the injector cleaning service while they are working on it. Will update once the workshop completes their inspection and repairs. The power loss and increased fuel consumption have been frustrating, so hoping this resolves the issues like it did in your case.