Audi S5's Engine Issues Point to Fuel System Failure

Recently dealt with similar symptoms on a 2014 Audi S4. The diagnosis revealed failed fuel injectors causing an inconsistent rich mixture. The oxygen sensor readings were all over the place, initially making it seem like an O2 sensor issue. Multiple warning signs matched your case: rough idle, poor acceleration, and the engine management light. The mass airflow sensor readings were normal, which helped narrow down the diagnosis. The fix required replacing two faulty injectors that were causing uneven fuel distribution. This is typically a serious issue that should be addressed promptly, as it can lead to catalytic converter damage if left unchecked. The problem originated from carbon buildup in the injectors, which is fairly common in direct injection engines. A proper repair includes testing all injectors, as they often fail in sequence rather than all at once. Worth noting the spark plugs should be inspected during this repair, as rich mixture conditions can foul them prematurely. Best to have a complete fuel system diagnosis done to prevent recurring issues.

Thanks for sharing your experience with the S4 fuel injector issue. Turned out my problem was pretty similar, uneven fuel distribution through faulty injectors causing a rich air-fuel ratio. I learned the hard way that the throttle body and intake manifold were clean, so the mass airflow sensor readings looked normal, but the actual problem was indeed with the injectors. Did you remember roughly what you paid for the complete fix? Also curious if youve had any related issues pop up since the repair?

Good to hear you got the injection valve issue sorted out. The mixture preparation error has been completely resolved since the repair, which matches my experience. The final bill came to 515 Euro for the complete fix, including labor and parts. The repair has held up perfectly with no related issues since. Your symptoms matched mine exactly, the mass airflow sensor readings were normal but the air-fuel ratio was way off due to the faulty injectors. The check engine light hasnt returned either. For anyone else reading this thread, when fuel injectors start failing, they often cause very similar symptoms: poor idle, weak acceleration, and engine management warnings. Getting it fixed promptly helps prevent damage to other components like the catalytic converter or oxygen sensors. A proper diagnosis is crucial since these symptoms can mimic other issues with the throttle body or intake system. The repair cost is significant but worth it to restore proper engine performance and prevent further problems.

Finally got the issue fixed. After getting my car diagnosed at a certified shop, turned out three of the injectors were clogged and needed replacement. Bill came to 790 Euro which hurt, but at least the car runs like new again. The mechanic showed me the old injectors, totally gunked up with carbon deposits. The repair took about 4 hours. They did a full fuel system cleaning while they were at it and checked the catalytic converter for any damage from the rich mixture. Luckily everything else looked fine. Really glad I didnt wait longer to get it fixed. The check engine light is gone, no more jerky acceleration, and idle is perfectly smooth now. The throttle response feels way better too, didnt realize how sluggish it had become. Thanks to everyone who helped point me in the right direction. Saved me from getting ripped off at my old mechanic who was trying to sell me a new throttle body and intake manifold I didnt need.