Audi Q3 Power Loss & Jerking: Knock Sensor Alert

I had a very similar issue with my 2018 Q2 2.0 TFSI. Being moderately experienced with car maintenance, I initially thought it was just bad fuel, but the symptoms persisted. The knock sensor was triggering constantly, which was causing the ECU to pull timing as a protective measure. This explained the power loss and jerking. After taking it to a workshop, they found significant carbon deposits in the combustion chamber, which were causing irregular detonation. The fix involved a complete combustion chamber cleaning service, including removal of carbon buildup from the valves. Total cost was 425 Euro, but it completely resolved the piston slap and power issues. The car has been running smoothly since the repair. Before suggesting specific solutions for your case, could you share: Current mileage, Fuel type regularly used, Service history, especially timing of last carbon cleaning, Exact fault codes showing up, Any recent changes in driving patterns or fuel source This information would help determine if your Q3 is facing the same underlying issue as mine did.

Last service was at 166814 KM and I appreciate your detailed input about similar symptoms. After looking into the fault codes more deeply, I noticed the engine knock sensor is indeed sending warning signals. I have been using regular 95 octane fuel, but maybe switching to higher grade fuel could help as a first step. The piston slap noise is most noticeable during cold starts and seems to improve as the engine warms up. Your suggestion about carbon deposits in the combustion chamber makes sense given my driving patterns are mostly short trips. I will schedule a diagnostic check to verify if cylinder heads need cleaning. The quoted repair costs in your case seem reasonable if it resolves these issues completely.

The carbon buildup issue definitely resonates with what I experienced on my Q2. After dealing with the problem and learning more, I discovered that pre-ignition issues are often linked to using lower octane fuel in these direct injection engines. Since switching to 98 octane, along with the cleaning service I mentioned, the engine tuning has remained stable with no knock sensor warnings. Short trips can definitely accelerate carbon accumulation because the engine never reaches optimal temperature for long enough. The cold start symptoms you describe match exactly what I dealt with, the piston slap noise is a telltale sign of carbon deposits affecting proper ignition timing. One tip from my experience: when you get the cleaning done, ask them to check the ignition coils too. In my case, they found one coil was weakening, which contributed to the combustion issues. The total repair ended up around 550 Euro including the coil replacement, but it was worth every cent for the restored performance. Looking back, I wish I had addressed the symptoms earlier before they worsened. Proper fuel grade and regular carbon cleaning are now part of my maintenance routine to prevent future issues.

Thank you for your helpful feedback about the knock sensor readings and carbon deposit theory. The connection between my short trips and potential carbon buildup makes a lot of sense. I have scheduled a full diagnostic inspection for next week and will specifically request they check the combustion chamber and ignition coils. In the meantime, I have already switched to 98 octane fuel based on your experience with pre-ignition issues. After just two tanks, the engine seems to be running slightly smoother, though the cold start detonation noise is still present. The workshop quoted me 600 Euro for a complete carbon cleaning service including ignition timing adjustment if needed. I will definitely make changes to my driving habits to help prevent future carbon accumulation. Instead of multiple short trips, I plan to combine errands into longer drives that allow proper engine tuning temperature. I appreciate you sharing your repair experience, it helped narrow down the likely cause and gave me confidence in pursuing the right fix.