Audi S5 Cold Start Misfire Needs Expert Diagnosis

Had the exact same symptoms on my 2013 Audi S4 last winter. The rough idle and hard starting pointed to fuel delivery issues, specifically with the injectors. The engine would struggle and misfire during cold starts, taking several minutes to smooth out. After diagnostics, it turned out multiple fuel injectors were failing. The fuel injection system had carbon buildup preventing proper fuel atomization during cold starts. This required removing and cleaning all injectors, plus replacing two that were beyond repair. This is a serious issue that needs addressing soon, as faulty injectors can: Cause increased fuel consumption, Lead to catalytic converter damage, Create more carbon deposits in other engine parts, Eventually prevent the car from starting altogether The fuel rail had to be removed to access all injectors. The repair involved specialized equipment for testing and cleaning. This isnt a DIY job due to the precise calibration needed for proper fuel delivery. Would strongly suggest having a certified shop perform a proper fuel system diagnosis. They should pressure test the fuel rail and check injector spray patterns to identify which ones are failing.

Had the exact same symptoms on my 2013 Audi S4 last winter. The rough idle and hard starting pointed to fuel delivery issues, specifically with the injectors. The engine would struggle and misfire during cold starts, taking several minutes to smooth out. After diagnostics, it turned out multiple fuel injectors were failing. The fuel injection system had carbon buildup preventing proper fuel atomization during cold starts. This required removing and cleaning all injectors, plus replacing two that were beyond repair. This is a serious issue that needs addressing soon, as faulty injectors can: Cause increased fuel consumption, Lead to catalytic converter damage, Create more carbon deposits in other engine parts, Eventually prevent the car from starting altogether The fuel rail had to be removed to access all injectors. The repair involved specialized equipment for testing and cleaning. This isnt a DIY job due to the precise calibration needed for proper fuel delivery. Would strongly suggest having a certified shop perform a proper fuel system diagnosis. They should pressure test the fuel rail and check injector spray patterns to identify which ones are failing.

Thanks for sharing your experience. I also had fuel injector issues on my Audi S5 that caused hard starting and rough idle problems. A professional injector test confirmed two faulty injectors alongside carbon buildup in the fuel system. Just wondering, do you recall roughly how much the repair cost in your case? I ended up paying around 1200 Euro for the complete injector cleaning and replacement work. Have you experienced any similar fuel delivery problems since the fix was done?

Thanks for sharing your experience. I also had fuel injector issues on my Audi S5 that caused hard starting and rough idle problems. A professional injector test confirmed two faulty injectors alongside carbon buildup in the fuel system. Just wondering, do you recall roughly how much the repair cost in your case? I ended up paying around 1200 Euro for the complete injector cleaning and replacement work. Have you experienced any similar fuel delivery problems since the fix was done?

The repairs on my S4 actually cost significantly less than yours, 515 Euro total for fixing one faulty cold start injector. The mechanic found the main issue was a single defective injection valve that was causing the rough idle and hard starting symptoms. Since having the work done six months ago, the fuel delivery system has been working flawlessly. No more cold start problems or rough idle issues. The engine fires up immediately and runs smooth from the first turn of the key, even on cold winter mornings. The fix was definitely worth every cent, as proper fuel delivery is crucial for engine longevity. The diagnostic equipment showed the other injectors were still in good condition, which helped keep the total cost down compared to needing multiple replacements like in your case. Your 1200 Euro repair sounds reasonable though, considering you needed two injectors replaced plus system cleaning. These modern direct injection systems are quite complex and require specialized equipment to service properly.

The repairs on my S4 actually cost significantly less than yours, 515 Euro total for fixing one faulty cold start injector. The mechanic found the main issue was a single defective injection valve that was causing the rough idle and hard starting symptoms. Since having the work done six months ago, the fuel delivery system has been working flawlessly. No more cold start problems or rough idle issues. The engine fires up immediately and runs smooth from the first turn of the key, even on cold winter mornings. The fix was definitely worth every cent, as proper fuel delivery is crucial for engine longevity. The diagnostic equipment showed the other injectors were still in good condition, which helped keep the total cost down compared to needing multiple replacements like in your case. Your 1200 Euro repair sounds reasonable though, considering you needed two injectors replaced plus system cleaning. These modern direct injection systems are quite complex and require specialized equipment to service properly.

Thanks for the input. Following the advice here, I took my S5 to a certified Audi specialist last week. The fuel system diagnosis revealed two failing injectors causing the cold start problems, plus significant carbon buildup throughout the injection system. The full repair came to 1200 Euro which included: Complete fuel injector cleaning service, Replacement of two faulty injectors, New seals and gaskets, Fuel system pressure testing After a week of driving, the engine misfire issues are completely gone. No more rough idle or hard starts in the morning. The engine fires up instantly and runs smooth from the start. Fuel consumption has also improved noticeably. While the cost was higher than expected, the improvement in performance made it worthwhile. Wish I had addressed these cold start problems sooner before the carbon buildup got so bad. Lesson learned about proper fuel system maintenance.

Thanks for the input. Following the advice here, I took my S5 to a certified Audi specialist last week. The fuel system diagnosis revealed two failing injectors causing the cold start problems, plus significant carbon buildup throughout the injection system. The full repair came to 1200 Euro which included: Complete fuel injector cleaning service, Replacement of two faulty injectors, New seals and gaskets, Fuel system pressure testing After a week of driving, the engine misfire issues are completely gone. No more rough idle or hard starts in the morning. The engine fires up instantly and runs smooth from the start. Fuel consumption has also improved noticeably. While the cost was higher than expected, the improvement in performance made it worthwhile. Wish I had addressed these cold start problems sooner before the carbon buildup got so bad. Lesson learned about proper fuel system maintenance.