Seat Leon Hybrid engine power loss and jerking

That sounds very similar to an issue I had with my Leon. I experienced reduced engine power and jerking when accelerating, though I didn't notice any smoke. Did you check for any error codes? In my case, it turned out to be engine knock, likely caused by detonation. Detonation, simply put, is when the air/fuel mixture in your cylinder ignites in an uncontrolled manner, instead of a smooth burn. This can be caused by several factors, including low-quality fuel or carbon deposits in the combustion chamber. Does the issue seem to resolve itself at higher RPMs?

Thanks for your quick reply. Yes, there is an error stored in the error memory! When you mention carbon deposits, how does that relate to engine tuning, and what are the dangers of continuing to drive with 'engine knock'? I am a bit worried about damaging something seriously, like the cylinder heads or causing 'piston slap'.

Yes, carbon deposits are a common culprit for engine knock, especially in direct injection engines like ours. Think of it like this: those deposits create hot spots in the combustion chamber that prematurely ignite the fuel-air mixture. As for your question about continuing to drive: prolonged engine knock can indeed cause serious damage. Piston slap, where the piston physically knocks against the cylinder wall, and damage to the cylinder heads are very real possibilities. I would strongly advise against pushing it. I would advise you take your car to a trusted mechanic to get a proper diagnosis and cleaning, or potentially a fuel additive to help. It sounds like you are describing exactly what happened with my car.

Thank you so much for the detailed information and your experience with this issue. It seems likely that I am facing the same problem. I took your advice and brought it to a workshop. As suspected, it was due to deposits in the combustion chamber. They cleaned it all up, and the car is running smoothly again. The repair cost me 425€. I appreciate your help!