T-Roc Engine Knocking: Common Causes & Troubleshooting

Had a similar issue with my 2015 VW Tiguan last summer. As someone with moderate experience working on VW engines, those symptoms immediately pointed to pre-ignition problems caused by carbon deposits in the combustion chamber. The symptoms matched exactly: engine knock during acceleration, power loss, and occasional smoke. The workshop confirmed extensive carbon buildup was causing irregular combustion and engine knock. They performed a thorough cleanup of the cylinder heads and combustion chamber, which resolved the issue completely. Total cost was 425€ including parts and labor. Before spending money though, could you share: Current mileage, Fuel type youre using, Maintenance history, Any recent engine tuning or modifications, When was the last time you had the fuel injection system cleaned These details would help determine if your issue is identical to what I experienced. In my case, regular maintenance and higher octane fuel since the repair have prevented the problem from recurring. The workshop mentioned these issues are somewhat common in direct injection engines, particularly when carbon deposits build up over time affecting combustion efficiency.

Last service was 2 months ago at 137128km. Thanks for sharing your experience. The symptoms do sound identical. Im using 95 octane fuel and have noticed the knocking gets worse when the engine is under load, especially during highway merging. No modifications or tuning have been done, and the injection system hasnt been cleaned since purchase. Pre-ignition seems like a strong possibility given the symptoms. The detonation issues combined with power loss definitely point toward carbon buildup affecting combustion timing. Your suggestion about checking the cylinder heads makes sense since poor combustion chamber conditions can lead to these exact problems. Will book a workshop appointment to have them inspect for carbon deposits and clean the system. The repair cost you mentioned seems reasonable for the work involved.

Having gone through this exact repair on my Tiguan, those additional details confirm my initial suspicion of carbon-related pre-ignition. The mileage and maintenance pattern matches what led to my issues. Switching to 98 octane fuel after the carbon cleanup made a noticeable difference in preventing detonation under load. The workshop explained that higher octane resistance helps manage pre-ignition, especially in direct injection engines prone to carbon buildup. A couple quick tips from my experience: Request a full inspection of the pistons while they clean the combustion chamber, Consider regular fuel system cleaning every 60000km to prevent future buildup, Monitor for any piston slap sounds after the repair, as carbon deposits can mask other issues The fact your knocking gets worse during highway merging matches my experience perfectly. Engine tuning wasnt necessary after the cleanup, but adding a fuel system cleaner additive every few tanks has helped maintain performance. Those occasional smoke issues should resolve completely once they address the carbon deposits affecting your combustion timing. Keep us posted on what the workshop finds.

Thanks for all the helpful advice. Based on your experience and the matching symptoms, I feel much more confident about the likely cause now. The knock sensor is probably working overtime trying to compensate for these pre-ignition issues. My engine knocking definitely mirrors what you described, especially during those high-load situations. The combustion chamber cleanup and inspection sounds like the right approach. Will schedule the service next week and make sure they do a thorough check of the pistons while cleaning out those carbon deposits. I appreciate the maintenance tips too. Moving to 98 octane fuel makes sense, and Ill definitely start using fuel system cleaner more regularly. Better to prevent future buildup than deal with reduced power and detonation issues again. Will update the forum once the workshop completes the repair and confirms if carbon deposits in the combustion chamber were indeed causing the pre-ignition problems. Thanks again for sharing your experience, it helped narrow down the diagnosis and saved me some diagnostic costs.