C70 diesel engine running lean

Sounds frustrating! I had a similar issue with my old Saab 9-3. Reduced power and rough running. It turned out to be a faulty mass air flow sensor causing the engine to run lean. Have you checked that or the intake manifold for any leaks?

Thanks for the tip! I haven't checked those specifically, but I did give the engine bay a quick look-over and didn't see anything obvious. Was your Saab's check engine light also on? And did it feel like a definite 'jerk' when you tried to accelerate?

Yep, check engine light was definitely on, and the acceleration was jerky, almost like it was struggling for fuel. Given your Volvo is a diesel, it could also be related to the EGR valve, oxygen sensor, or even the catalytic converter. But honestly, with those symptoms, and the low mileage, it's probably best to get it checked by a professional. Could save you a lot of headache.

Thanks a lot for your help! I took it to the shop, and you were right – it turns out an injection valve/injector was defective and causing the lean running condition. Cost me 515€ to get it fixed, but at least it's running smoothly again!