Audi Q2 Power Loss and Knocking Signals Major Engine Trouble

I experienced nearly identical symptoms with my 2019 Audi Q3, which has a similar engine configuration. With some experience working on modern engines, I can relate to this concerning situation. The knock sensor in my case was indeed triggering due to carbon deposits in the combustion chamber, causing improper ignition timing and engine knock. The symptoms matched yours exactly, power loss, jerking, and that distinctive knocking sound during acceleration. I took it to an independent workshop specializing in fuel system cleaning. They performed a thorough combustion chamber cleaning, adjusted the ignition timing, and reset the engine management system. Total cost was 425 Euro, but it completely resolved the issues. The engine ran smoothly afterward with proper fuel octane. To provide more specific advice for your case, could you share: Current mileage, Fuel type typically used, When was the last fuel system service, Does the problem occur more when the engine is cold or warm, Any recent changes in driving patterns or fuel brand These details would help determine if your Q2 is facing the same underlying problem. Engine knock can have multiple causes, and proper diagnosis is crucial for effective treatment.

Thanks for sharing your experience. My vehicle currently has 67028 KM on the odometer with the last major service completed just last month where they performed routine engine tuning. The issues actually started after switching to a lower grade fuel, which likely triggered the knock sensor warnings. The piston slap sound is most noticeable when the engine is cold, particularly in the morning. This seems to match with your description of carbon deposit issues in the cylinder heads. I will try switching back to higher octane fuel first to see if it makes any difference before taking it to a specialist. The symptoms being so similar to what you experienced gives me a good starting point for diagnosis.

Thanks for those additional details. The fuel grade switch definitely explains the symptoms. When I had my Q3 issue, I also noticed the piston slap was much worse with lower octane fuel, especially during cold starts. The knock sensor is likely reacting to the improper combustion timing caused by the lower grade fuel in the combustion chamber. Modern engines are precisely tuned for specific octane ratings, and downgrading fuel can trigger protective measures in the engine management system. In my case, switching back to premium fuel only partially solved the issue because carbon deposits had already accumulated. The full combustion chamber cleaning was necessary to restore proper performance. Since your symptoms started specifically after the fuel switch, you might have better luck just returning to the correct octane rating. Consider doing a fuel system cleaner additive treatment alongside the higher octane fuel. This helped clear minor carbon buildup in my engine before requiring the full professional service. Regular engine tuning is important, but fuel quality plays an equally crucial role in preventing knock sensor-related issues. Keep monitoring for improvement after switching fuel grades. If symptoms persist beyond a few tanks of proper fuel, professional cleaning might be needed like in my case.

Thank you for the detailed feedback on the fuel and knock sensor connection. Your experience with your Q3 has been quite helpful. Based on your suggestion, I filled up with premium fuel yesterday and added a fuel system cleaner. After about 200KM of driving, the engine knock sounds have already decreased noticeably during cold starts. The pre-ignition issues seem less frequent, though not completely gone. My morning commute today was much smoother with less jerking during acceleration. The engine tuning from last month combined with proper fuel grade appears to be making a positive difference. I will continue monitoring for the next few tanks and schedule a professional cleaning if the knock sensor warning persists. The repair costs you mentioned of 425 Euro for a full system cleaning seem reasonable if it comes to that. For now, I am hopeful the switch back to premium fuel will resolve most issues before carbon deposits become a major problem. Thanks again for helping me understand the likely root cause with the fuel grade change.