RS6 Engine Misfire Troubles: Rough Idle and Power Loss

Having a similar level of symptoms with my 2007 RS4, which shared many components with your model. I have some experience working on these engines. The check engine light and misfiring symptoms turned out to be caused by a faulty fuel injector. There was rough idling, power loss, and significant jerking during acceleration, exactly what you describe. The engine management system detected the cylinder misfire which triggered the warning light. After diagnostic testing, the workshop found one defective injection valve that was not delivering fuel properly. The repair involved: Complete diagnostics scan, Injector removal and testing, Replacement of the faulty injector, System reprogramming Total cost came to 515 Euro including parts and labor. The fix completely resolved all symptoms and the engine runs smoothly now. To provide more specific guidance: What error codes is your engine throwing? Have you noticed if the misfiring seems worse when the engine is cold or at operating temperature? Also, when did these symptoms first appear, suddenly or gradually? This could also be related to ignition coils or fuel pump issues, but the symptoms you describe match my injector experience quite closely.

Thanks for the helpful response. After my latest service at 44520 KM, the workshop pulled error codes P0301 and P0303, indicating misfires in cylinders 1 and 3. The spark plugs were replaced just 5000 KM ago. The symptoms started gradually over about two weeks. The throttle response issues and rough running are definitely worse when the engine is cold. Once warmed up, the cylinder misfire seems less noticeable, but the check engine light stays on consistently. Based on your experience with the fuel injector issue, I will have those tested. The repair cost you mentioned seems reasonable compared to what I was expecting. Have scheduled a diagnostic appointment to confirm if its injectors or possibly a failing fuel pump causing these issues.

Thanks for the update on those error codes. The cold-start symptoms you describe are very similar to what I experienced with my RS4, strengthening my suspicion of fuel injector problems. In my case, cylinders 2 and 4 were the trouble spots, but the behavior matches exactly, worse throttle response and rough running during cold starts. When my workshop did further testing, they found uneven fuel spray patterns from the affected injectors. The fact that your spark plugs are relatively new makes injector issues even more likely as the root cause of the cylinder misfire problems. A failing fuel pump would typically cause more consistent issues regardless of engine temperature, whereas the cold-start emphasis points strongly toward injector problems. The check engine light behavior also aligns with my experience, it stayed on constantly until the faulty injectors were replaced. One thing to note, while my repair cost was 515 Euro, with two cylinders affected you might be looking at closer to 800 Euro. Make sure the workshop performs a complete fuel system pressure test to rule out any fuel pump concerns before focusing on the injectors. Keep us posted on what the diagnostics reveal. There are quite a few RS6 owners here who have dealt with similar engine misfiring issues.

Based on the conversation flow, here is a natural conclusion from the original poster's perspective: Really appreciate all the detailed input. Just got back from the workshop and you were spot on, they confirmed issues with both fuel injectors in cylinders 1 and 3. The combustion misfire is definitely caused by inconsistent fuel delivery, matching the symptoms you described. The complete diagnosis showed normal fuel pump pressure, but both injectors are showing irregular spray patterns during testing. Total quote came in at 780 Euro for replacing both injectors, which aligns with your cost estimate. The rough idle is particularly noticeable during cold starts, exactly as mentioned. Will have them do the full repair next week, including cleaning the fuel rails while they have everything apart. The constant engine misfiring and poor throttle response should be resolved once the new injectors are installed. Thanks again for your help in narrowing down the issue. I feel much more confident now knowing this is a fairly common problem with a straightforward fix. Will update once the repair is complete.