S60 Engine Running Rich

I understand you are experiencing difficulties with your S60. If the engine is indeed running excessively rich, several factors could potentially contribute to this condition. Have you inspected the intake manifold for any potential obstructions or leaks? A malfunctioning catalytic converter may also create similar symptoms. It's plausible that a defective injector is the culprit, causing an oversupply of fuel into the combustion chamber. Have you observed any unusual exhaust odors accompanying the aforementioned symptoms?

Thanks for the reply! I haven't checked the intake manifold yet, but I'll definitely take a look. I haven't noticed any weird smells from the exhaust, though. Could a bad injector really cause all these problems? Is there a way to test them without taking everything apart?

Indeed, a malfunctioning fuel injector can precipitate the array of issues you described. While a comprehensive diagnosis necessitates specialized equipment, it is advisable to seek counsel from a qualified technician. In my experience, similar symptoms in my S60 were attributed to a faulty fuel injector which resulted in excessive fuel delivery and inefficient combustion. Therefore, a professional assessment is recommended to ascertain the definitive cause and implement the appropriate remedial measures.

Took it to the shop, and you were spot-on! It was a defective fuel injector. They replaced it, and now everything is running smoothly again. Cost me 515€, but at least the car is back to normal. Thanks for the help!