VW Eos Engine Knocking: Timing & Sensor Issues Alert

I dealt with very similar symptoms on my 2012 VW Golf GTI last year. Having moderate experience with engine issues, these symptoms immediately concerned me because of potential engine knock and detonation risks. The diagnosis revealed carbon deposits in the combustion chamber, which were causing irregular combustion and false knock sensor readings. The cylinder heads needed thorough cleaning to resolve the issue. The repair process involved: Complete fuel system cleaning, Removal and cleaning of cylinder heads, Replacement of spark plugs, ECU recalibration, Higher grade fuel recommendation (95 to 98 octane) Total cost came to 425€, which included parts and labor. Since the repair, no more power loss or smoke issues, and the engine runs smoothly again. To better assist with your Eos issue, could you share: Current mileage, Fuel grade typically used, When symptoms first appeared, Whether issues occur more during cold or hot engine, Any recent maintenance history These details would help determine if your issue matches what I experienced or if it might be something different requiring alternate solutions.

Thanks for sharing your experience. My Eos has 49794km and just had its annual service last month. After trying your suggested fix with higher octane fuel (98), the engine knock persists. The detonation sounds are most noticeable during warm-up. The combustion chamber cleaning suggestion makes sense given my symptoms, but I wonder if the knock sensor itself might be faulty since the issue started quite suddenly after the recent service. Going to get the cylinder heads checked out this week based on your feedback. Hopefully fixing these issues now prevents more serious engine damage.

Thanks for the update on your Eos. The sudden onset after service actually matches what happened with my GTI, the timing seems more than coincidental. While my carbon deposit issue was resolved with the cleaning, I had a subsequent problem where the knock sensor itself was giving false readings. The warm-up detonation you mentioned is particularly telling. After my initial repair, I discovered the knock sensor had been damaged during the service, causing similar symptoms. The pre-ignition issues during warm-up are classic signs of a faulty knock sensor rather than just carbon buildup. For reference, my final fix included: Replacing the knock sensor (85€), Adjusting ignition timing, Reprogramming the ECU to factory settings After these additional steps, the engine knock completely disappeared. Given your symptoms started post-service, I suggest having them specifically check the knock sensor wiring and mounting. A loose or damaged sensor can trigger false detonation readings, causing the ECU to pull timing unnecessarily. Keep using the higher octane fuel for now, it provides protection against engine knock while you diagnose the root cause.

Thanks for the input. After comparing my symptoms with these experiences, I scheduled a diagnostic appointment focusing on both the knock sensor and potential carbon buildup in the combustion chamber. The timing of my issues appearing right after service does suggest possible sensor damage during maintenance. The engine knock symptoms remain most noticeable during warm-up, even with the switch to higher octane fuel. While using premium fuel hasnt fully resolved the detonation, it seems to have slightly reduced the severity of the power loss and jerking under acceleration. Will update once the cylinder heads are inspected and the knock sensor is tested. Really hoping this catches the problem before any serious engine damage occurs from prolonged pre-ignition issues. The repair costs shared here at least give me a reasonable estimate of what to expect if similar work is needed on my Eos.