VW Taigo Engine Knocking Causes Performance Drop

I had a very similar issue with my 2019 VW T-Cross with the 1.0 TSI engine. As someone with some experience working on VAG engines, those symptoms immediately pointed to combustion chamber deposits, which was causing pre-ignition problems. My engine was also experiencing power loss and rough running. After taking it to a specialist workshop, they confirmed deposits had built up in the combustion chamber, leading to irregular detonation and poor engine performance. The fix involved: Complete combustion chamber cleaning, New spark plugs, Engine tuning to adjust timing, Fuel system cleaning Total cost was 425€ and it completely resolved the issues. The engine ran like new afterward with no more piston slap or knocking. Before suggesting specific solutions for your case, could you share: Engine size and type, Current mileage, Service history details, Type of fuel typically used, When the symptoms first appeared This information would help determine if your issue matches what I experienced and provide more targeted advice.

Last service was at 50000km and symptoms started about 2 weeks ago. I am getting really worried about potential cylinder heads damage from prolonged detonation. The repair cost estimate I got for a complete check and repair was 680€. The diagnosis so far points to carbon deposits causing pre-ignition. My mechanic wants to do compression testing and inspect the combustion chamber with a borescope before proceeding with repairs. The fuel octane is correct for my engine but maybe the carbon buildup is affecting combustion. Will engine tuning be needed after cleaning? I want to make sure any fix addresses the root cause to prevent recurrence.

Having gone through this exact issue with my T-Cross, I can confirm compression testing and borescope inspection are crucial steps. The 680€ estimate sounds reasonable considering the diagnostic work needed. The knock sensor readings on my vehicle were indicating detonation events, which prompted similar concerns about cylinder head damage. However, after the thorough cleaning and diagnostic process, no permanent damage was found in my combustion chamber. Engine tuning was definitely necessary after the cleaning procedure in my case. The ECU parameters needed adjustment to optimize timing and prevent knock events with the clean combustion chamber. My workshop explained that carbon deposits can change combustion characteristics, so returning to factory-spec conditions requires recalibration. A few key points from my experience: The cleaning process resolved the piston slap symptoms completely, Fuel octane remained unchanged but combustion improved significantly, Regular carbon cleaning intervals are now part of my maintenance schedule, Engine performance returned to factory specifications after tuning Consider requesting documentation of the borescope inspection results. This will give you a baseline for future reference and confirm the extent of any deposits.

Thanks for the detailed responses. After talking with my mechanic again today, I have decided to proceed with the full diagnostic and repair package including the borescope inspection. The symptoms match exactly what you experienced with pre-ignition issues from carbon deposits. My main concern was potential long-term engine damage, but hearing that your knock sensor readings were similar and no permanent damage was found is reassuring. I will definitely get the engine tuning done after cleaning to ensure everything is properly calibrated. The 680€ estimate seems fair considering the work involved. I plan to add regular carbon cleaning to my maintenance schedule once this is fixed to prevent these issues from recurring. Will also keep records of the borescope inspection as suggested. Having dealt with the same piston slap and performance problems, your experience has been really helpful in understanding what to expect from the repair process. I appreciate you taking the time to share the details of your diagnosis and resolution. Will update once the work is completed to confirm if the combustion chamber cleaning and engine tuning resolved the knock issues completely.