Skoda Superb Diesel Engine Running Rich

That sounds familiar! I had a similar issue with my Skoda Superb (though not the same year). Reduced power and rough running are classic signs of a fuel mixture problem. Have you checked your oxygen sensor? A faulty one can really mess with the fuel/air ratio. Also, when was the last time you replaced your air filter and spark plugs? A clogged air filter can definitely cause a rich running condition. A rich condition can damage your catalytic converter over time, so it's important to get it sorted quickly. It also affects fuel economy.

Thanks for the quick reply! I haven't checked the oxygen sensor myself, to be honest I'm not even sure where to find it. The air filter was replaced about a year ago, and I haven't touched the spark plugs since I bought the car. Could it really be just the spark plugs causing all these issues? What does "rich condition" mean exactly?

Okay, so "running rich" means your engine is getting too much fuel compared to air. Spark plugs are less likely to be the sole cause, though old ones won't help. The oxygen sensor measures the oxygen in your exhaust and tells the engine computer (ECU) how to adjust the fuel mixture. If it's faulty, the ECU gets bad information and can dump too much fuel into the engine. Given your symptoms and the age of the car, a defective injector is a strong possibility. Honestly, without proper diagnostic tools, it's tough to pinpoint the exact problem. I'd recommend taking it to a workshop with experience in diesel engines. They can run proper tests and figure out which injector is failing.

Took your advice and brought it to a trusted mechanic. Turns out you were spot on! It was indeed a defective fuel injector. Replacing it cost me around 515€, which is a bummer, but the car runs like new again. No more jerking, and the check engine light is finally off. Thanks a bunch for your help!