Audi S3 Cold Start Nightmare: Injector Issues Explained

Had a similar situation with my 2018 Audi S4, and after some troubleshooting, it turned out to be injector-related. I have some experience working on cars, mainly basic maintenance and diagnostics. The symptoms were nearly identical, hard starting issues and rough idle during cold starts. The engine would eventually smooth out after warming up, but those first few minutes were concerning. The workshop conducted a thorough injector test and fuel rail pressure check. They found one faulty injector that wasnt atomizing fuel properly during cold starts, leading to the engine misfire symptoms. The diagnostic process involved: 1. Complete fuel system pressure testing 2. Individual injector flow rate measurements 3. Electronic diagnostic scan 4. Cold start monitoring The repair involved replacing the problematic injector and performing a full system cleaning. Total cost was 515 Euro, which included parts, labor, and diagnostic time. Before suggesting specific solutions, could you share: Any check engine lights or error codes? Does fuel pressure hold after shutting off engine? How many kilometers on your current injectors? Have you noticed any changes in fuel consumption? This information would help determine if your issue matches what I experienced and whether similar solutions might work for your S3.

Last service completed at 177052KM. Your experience sounds identical to my fuel system troubles. The CEL started flickering during cold starts last week. Fuel consumption increased by about 15% over the past month. When checking fuel pressure using my scan tool, I noticed it drops faster than normal after shutoff. Originally thought it might be the fuel pump, but based on your symptoms and resolution, will have the injectors tested first. The hard starting issues definitely point toward fuel injection problems. Appreciate the detailed diagnostic steps. Will schedule an appointment to have them test the injectors and fuel rail pressure. The cost seems reasonable for a proper fix rather than just throwing parts at it.

Thanks for providing those details about the fuel consumption increase and pressure drop. The symptoms you're describing, especially the fuel pressure loss after shutdown, strongly align with what I experienced with my S4's failing injector system. The hard starting issues combined with the check engine light during cold starts is a classic sign of fuel injection problems. When my injector was failing, I also noticed that same 10-15% increase in fuel consumption before getting it fixed. One thing I noticed after my repair, the engine misfire issues completely disappeared during cold starts. The workshop mentioned that faulty injectors often show their worst symptoms during the cold start phase when precise fuel atomization is most critical. Given your vehicle's mileage and the similar pattern of fuel system issues, having the injectors tested is definitely the right approach. Make sure they perform the complete fuel rail pressure test since the pressure drop you mentioned could indicate related issues in the fuel delivery system. Quick note about the repair, after replacing my faulty injector, they recommended preventive cleaning of the remaining ones to ensure balanced fuel delivery. This added about 85 Euro to the total but helped prevent future cold start problems.

Given the details of your car's condition and hearing about your experience, will definitely request the complete testing package you mentioned. The symptoms match almost perfectly, engine misfire during cold starts, increased fuel consumption, and that telling pressure drop. Never thought to monitor the fuel rail pressure after shutdown until you mentioned it, but that diagnostic reading really seems to confirm the fuel delivery issues. The flickering CEL during cold starts tracks with your injector problem too. Planning to book the service next week and will request both the pressure testing and injector flow measurements. The 515 Euro repair cost plus 85 Euro for preventive cleaning sounds worth it to fix these cold start problems properly. Much better than replacing unusual parts hoping to solve it. Will make sure they do the complete fuel system diagnosis including the fuel rail tests you suggested. Makes sense to check the entire fuel delivery system while they have it apart. Really appreciate the detailed information about the testing process and what to expect.