Audi S1 Cold Start Issues, Fuel Delivery Diagnosis

Had almost the exact same issue with my 2016 Audi S3. Started with hard starting problems, especially in the morning, followed by a really rough idle for the first few minutes. After some initial fuel system cleaning attempts, the workshop diagnosed a faulty fuel injector that was causing inconsistent fuel delivery. The repair involved: Complete diagnostic scan, Fuel pressure testing at the fuel rail, Removing and testing all injectors, Replacing one defective injector, Programming the new injector to the ECU Total cost came to 515 Euro and solved the engine misfire issues completely. The hard starting problems disappeared right away. As someone with moderate experience working on cars, I initially thought it might be something simpler like bad fuel or a clogged filter, but the systematic testing by the workshop proved essential for finding the actual cause. To provide more specific advice about your S1: What error codes is it showing, if any? Does the rough idle improve once the engine warms up? Have you noticed any changes in fuel consumption? Are there any other symptoms like hesitation during acceleration?

Just had my 161053 KM service and can confirm this was a fuel injector issue. The mechanic performed an injector test that showed inconsistent spray patterns. The rough idle and hard starting were identical symptoms to yours. The fuel rail pressure tested normal but one injector was definitely the culprit. After replacement and ECU adaptation, the cold start problems cleared up completely. Cost was 480 Euro including parts and labor. Fuel consumption returned to normal and the engine runs smoothly from startup. Would recommend getting a proper fuel system diagnosis rather than trying simpler fixes first, saves time and money in the long run. The repair took about 4 hours total.

Thanks for the follow-up on your S1 repair. Your experience matches exactly what I went through with my S3 injector replacement. The diagnostic approach was spot-on, testing the spray patterns is crucial for identifying inconsistent fuel delivery issues. The repair cost sounds about right, I paid slightly more at 515 Euro but prices can vary. Good call on getting the ECU adaptation done too; skipping that step can lead to rough idle issues even with new injectors. Interesting that your fuel rail pressure tested normal, just like mine. This really shows how fuel injection problems can exist even with proper system pressure. The cold start problems are often the first sign something is off with the injectors. One tip for anyone else reading: tracking fuel consumption changes can be an early warning sign of injector issues. In both our cases, fixing the faulty injector restored normal fuel economy alongside solving the rough idle and starting problems. 4 hours labor time is typical for this repair considering the diagnostic work and programming needed. Have you noticed any difference in engine noise during cold starts now?

Good morning! The mechanic performed another injector test and cold start check this morning, everything is still working perfectly after 3 weeks. No more engine misfire issues during startup. You were spot on about monitoring fuel consumption. Looking back at my fuel logs, I was using about 12% more fuel in the months before the repair without realizing it. The rough idle and hard starting were the obvious symptoms, but the gradual increase in fuel usage was a clear warning sign I missed. Engine noise is now completely normal from cold start, no more rattling or uneven running. The difference is dramatic compared to before. When I think about the time I spent trying fuel system cleaners and new filters, I should have gone straight for proper diagnostics. Total repair cost was worth every cent considering how smoothly everything runs now. Really appreciate the detailed insights you shared, helped me better understand what I was dealing with and gave me confidence in the repair approach. Time to mark this one solved. Anyone else experiencing similar cold start symptoms should definitely get their injectors tested early on.