Rough Cold Start? Bad Injector May Be the Culprit

I had a very similar issue with my 2006 Audi A3 2.0T. Having worked on several fuel system issues before, I recognized the symptoms immediately. The rough idle and engine misfire during cold starts were identical to what you describe. The fuel system showed inconsistent pressure at the fuel rail during diagnostics. After testing, a faulty injector was confirmed as the culprit. Initially tried injector cleaning service, but it only helped temporarily. The workshop eventually found that one injector was completely defective and needed replacement. The total repair came to 515 Euro, including parts and labor. The fix completely resolved the cold start issues and eliminated the rough running condition. Fuel delivery returned to normal and the engine now runs smoothly from startup. Before suggesting specific solutions for your case, could you provide: Engine size and type, Current mileage, Check engine light status, Any stored error codes, Recent fuel system maintenance history, Whether problems occur only during cold starts or also when warm This information would help determine if your situation matches what I experienced and ensure appropriate recommendations.

Current mileage is 194720 KM. The service history shows the last fuel injection system maintenance was completed 25000 KM ago. I checked for error codes using an OBD scanner and found P0201 and P0203 indicating cylinder 1 and 3 injector circuit malfunctions. The check engine light comes on intermittently, usually during cold starts. When warm, the engine runs much better with only occasional hesitation. The rough idle and misfiring are definitely worst during the first 5 minutes of operation, especially in cooler weather. I already tried using fuel system cleaner additives but saw no improvement. Planning to have a proper injector test done to check spray patterns and flow rates. The fuel delivery issues seem to point toward multiple failing injectors rather than just one.

Thanks for providing those details. Seems your A4 has multiple injector issues, similar to what I encountered with my A3, though yours appears more extensive. Those P0201 and P0203 codes confirm what I suspected, you are dealing with multiple failing injectors showing circuit malfunctions. The fuel injection system behavior matches my previous experience, though I only had a single bad injector to contend with. The cold start issues and rough running during warmup suggest the fuel rail pressure may be inconsistent, which I also experienced. However, with two confirmed faulty injectors, a complete fuel system diagnosis is crucial before proceeding with repairs. When my single injector failed, the repair cost was 515 Euro. With multiple injectors needing replacement, you should budget accordingly. Based on my experience, I would recommend: 1. Full fuel system pressure testing 2. Individual injector flow rate measurement 3. Replace both faulty injectors as a set 4. Consider cleaning the remaining injectors while system is opened Hard starting issues and rough running during the cold start phase were completely resolved after my repair. Given the similar symptoms but more extensive nature of your problem, addressing both injectors should provide comparable results. Would you like specific information about the diagnostic tests performed on my car before the injector replacement?

Thanks for sharing those test results, multiple failing injectors definitely explains my cold start problems. Having P0201 and P0203 codes matches the symptoms perfectly. Now I know why fuel delivery has been so inconsistent. I will move forward with getting the full diagnostic testing done. Given the high mileage and existing codes, replacing both faulty injectors makes sense rather than attempting more cleaning. The fuel rail and entire injection system should be checked too since everything is connected. Based on your repair cost of 515 Euro for one injector, I will budget around 1200 Euro to cover parts and labor for both injectors plus testing. Cold start issues are too annoying to keep living with, especially in cooler weather. Yes, I would appreciate details about your diagnostic process. That will help me know what to expect when I take it to the shop. I want to ensure they do thorough testing before replacing components.