Audi Q2 Rich Fuel Mix Causes Power Loss & Rough Idle

Having experienced almost the exact same symptoms with my 2016 Audi Q3, I can share my journey with this issue. With some experience working on fuel system problems, I recognized these classic signs of poor fuel economy and rich mixture concerns. The check engine light was my first indicator, and the symptoms matched yours precisely, rough running, sluggish acceleration, and excessive fuel consumption. The air-fuel ratio was clearly off, which prompted a thorough diagnostic check. In my case, one fuel injector was faulty, causing an inconsistent spray pattern and flooding that cylinder with excess fuel. The workshop performed injector testing and found one injector was stuck partially open, preventing proper atomization. The repair involved: 1. Complete diagnostic scan 2. Fuel injector removal and testing 3. Replacement of the defective injector 4. System cleaning 5. Reset of fuel trim values Total cost came to 515 Euro including parts and labor. Since the repair, fuel economy returned to normal and the engine runs smoothly again. To provide more specific advice for your Q2, could you share: Current mileage? When was the last fuel system service? Are there any unusual sounds when accelerating? Has the catalytic converter been checked recently? These details would help determine if your situation mirrors what I experienced with my Q3.

Just had my car serviced at 172624 KM and can confirm the oxygen sensor was indeed the main culprit. The repair shop found a faulty sensor causing incorrect air-fuel mixture readings. After replacing both upstream and downstream oxygen sensors, my fuel economy improved dramatically and the check engine light cleared. The rough running and power issues disappeared completely. They also checked the spark plugs and air filter during diagnostics, but these were still in good condition. The total fix cost 380 Euro including parts and labor. If you are experiencing similar problems, definitely have the oxygen sensors tested first before exploring more complex fuel system repairs.

Thanks for the update about your Q2. That matches what I discovered on my Q3 after further diagnosis, it turned out the faulty injector I mentioned earlier was actually a secondary issue caused by a bad oxygen sensor sending incorrect signals to the ECU. When the oxygen sensor fails, it cant properly measure the air-fuel ratio, leading the engine to run rich. This rich mixture not only wastes fuel but can potentially damage the catalytic converter over time. The symptoms you described, poor fuel economy, rough running, and reduced power, are textbook indicators of a failing oxygen sensor. The 380 Euro repair cost seems reasonable, and replacing both sensors was a smart preventive move. Like you, my fuel consumption dropped significantly after the fix, and the engine performance returned to normal. This confirms that with these specific symptoms, checking the oxygen sensors should be the first diagnostic step rather than jumping straight to fuel injector replacement. It saves both time and money, especially since sensor replacement is typically less expensive than major fuel system work.

I appreciate everyone sharing their experiences here. Quick follow-up on my case, after driving about 1000km since the oxygen sensor replacement, I can report the repair has fully resolved all issues. The check engine light has stayed off, and fuel economy is back to normal levels. For anyone searching the forum with similar symptoms: rough running, poor fuel economy, and rich mixture issues, definitely have your oxygen sensors tested first. The diagnostic process was straightforward, and the repair cost of 380 Euro proved to be a worthwhile investment. What really convinced me the issue was fixed was the immediate improvement in acceleration response and how smoothly the engine now runs. Also discovered during this process that regular air filter maintenance plays a key role in preventing false readings from the oxygen sensors. Glad I asked here before assuming I needed more extensive fuel injector repairs. This turned out to be a much simpler fix than initially feared.