Touareg Hybrid Engine Knock Signals Major Performance Drop

Having some experience with hybrids, I dealt with a similar issue on my 2020 Tiguan eHybrid that shares many components with your Touareg. The symptoms you describe match exactly what I experienced, reduced power, jerking, and knock sensor warnings. The root cause in my case was carbon deposits in the combustion chamber, which led to pre-ignition issues. This created irregular combustion patterns that the knock sensor was picking up. The cylinder heads needed a thorough cleaning to resolve the issue. The repair cost me 425€ including parts and labor. The workshop performed: Complete diagnostic scan, Combustion chamber cleaning, Knock sensor verification, ECU reset and adaptation The piston slap sounds you mention could indicate the same issue, but to provide more specific guidance, could you share: Current mileage, Fuel type you typically use, When the symptoms first appeared, Whether the issue occurs more during cold starts These details would help determine if your case mirrors what I experienced with my Tiguan. Regular carbon buildup is common in direct injection engines, but the timing of symptoms can indicate if other factors are involved.

Thanks for sharing your experience. Since my last service at 75000km, I have been running higher fuel octane (98) to help minimize any pre-ignition issues. The knocking sounds started about 2 weeks ago, mainly during warm-up. I noticed the combustion chamber problems are worse when the engine is under load, especially during acceleration. The workshop quoted 850€ for a complete diagnosis and cleaning of the cylinder heads, which seems high compared to your repair costs. Based on your feedback, I will have them check the knock sensor thoroughly since the symptoms match so closely. Did you notice any improvement in fuel consumption after the repair?

Your case sounds very familiar and brings back memories of my repair experience. Using 98 octane is definitely a smart move, though in my case the carbon buildup occurred despite using premium fuel. The price difference is likely because Touareg engine work typically costs more than Tiguan repairs due to the complexity of the hybrid system and engine placement. That said, 850€ seems slightly high, might be worth getting a second quote. Regarding fuel consumption, I saw a noticeable improvement after the repair. Engine tuning and ignition timing were properly restored once the carbon deposits were cleared, resulting in about 0.8L/100km better efficiency. The engine also ran much smoother, especially during cold starts. One important note from my experience: make sure they perform a complete cylinder heads inspection while doing the cleaning. In my case, they found minor scoring that could have led to bigger issues if left unchecked. The pre-ignition problems completely disappeared after the repair, and the knock sensor stopped triggering false readings. If the knocking is mainly during warm-up, this strongly suggests carbon deposit interference with proper combustion, just like in my case. The complete fix restored normal operation and eliminated all those worrying symptoms. The engine has run perfectly for 30000km since the repair.

Thanks for providing such detailed insight into similar hybrid repairs. I feel more confident about the diagnosis now. The warm-up knocking and load-related combustion chamber issues match exactly what you experienced. I will get a second quote since 850€ does seem steep, though I understand the Touareg hybrid system complexity adds to costs. Your feedback on improved fuel consumption after fixing the ignition timing issues is encouraging. I appreciate the tip about having them thoroughly inspect the cylinder heads during cleaning. I will specifically request they check for scoring while addressing the piston slap and carbon deposits. Knowing your engine has run perfectly for 30000km post-repair gives me confidence this is the right path forward. I will continue with the higher fuel octane even after repairs. I will update the forum once I have the work completed and can confirm if it fully resolved my engine knock sensor warnings and performance issues.