Tiguan Engine Knock & Power Loss: Sensor/Timing Issues

Had similar issues with my 2015 VW Golf GTI. The symptoms matched exactly, drop in power, jerking, and visible exhaust smoke under acceleration. After inspection, it turned out carbon deposits had built up in the combustion chamber, affecting ignition timing and causing detonation. The root cause was using lower fuel octane than recommended, combined with frequent short trips that prevented the engine from reaching proper operating temperature. The deposits created hot spots in the cylinder heads, leading to pre-ignition and engine knock. The fix required: Complete fuel system cleaning, Removal and cleaning of cylinder heads, Replacement of spark plugs, ECU reset and timing adjustment This was a serious issue that needed immediate attention since continuous detonation can damage engine components. The piston slap symptoms disappeared after the repair. Running premium fuel since then and ensuring the engine warms up properly on each drive has prevented the issue from returning. Suggest having a qualified technician perform compression testing and inspect the fuel system. The symptoms point to either carbon buildup or timing-related problems that should be addressed quickly to prevent engine damage.

Thanks for sharing your GTI experience. Sounds exactly like what I am dealing with in my Tiguan. The engine knock symptoms and pre-ignition issues match perfectly. Good to know about the carbon deposits since I also tend to make lots of short trips. Can you remember roughly how much you paid for the complete repair job? Also curious if you had any other issues pop up after the fix was done? Planning to take mine in next week and want to budget accordingly, especially since the cleaning and knock sensor inspection might be needed.

The repair costs came to 425€ for cleaning out the carbon deposits in the combustion chamber and all related work. Since having this done six months ago, the engine knock and pre-ignition issues completely disappeared. The engine tuning after the cleaning made a huge difference in performance. The shop found significant carbon buildup, similar to what you described with your Tiguan. Once they cleared the deposits and recalibrated everything, the car runs like new again. No other problems have surfaced since the repair. To prevent future issues, I now use higher octane fuel and let the engine warm up properly before driving. The piston slap and rough running are completely gone. Money well spent considering how much damage continued knocking could have caused to the engine components. Just make sure your shop does a thorough inspection of the fuel system and knock sensors while they have it apart. Catching these combustion chamber issues early saved me from more expensive repairs down the road.

I took my Tiguan to the shop yesterday after reading about your experience. The mechanic confirmed the carbon buildup in the combustion chamber was causing the engine knock. They did a full cleaning service, adjusted the ignition timing, and checked the knock sensors. Total bill came to 390€, which included: Combustion chamber cleaning, New spark plugs, Fuel system flush, Engine tuning adjustment The difference is remarkable. No more jerking or smoke, and the engine runs smooth again. The shop explained that using better fuel octane and proper warm-up would prevent future buildup. They also showed me the carbon deposits they cleaned out, pretty shocking amount for a relatively new car. Will definitely keep an eye on the symptoms and stick to premium fuel from now on. Really glad I caught this early before any serious engine damage occurred. The engine knock is completely gone and power delivery feels like new again.