Eseries VANOS issue

Interesting. I had a similar issue with my old BMW 3 Series, also a diesel. The check engine light was on constantly, and the fuel economy went down. In my case, it was oil sludge buildup affecting the VANOS system. The variable timing wasn't working correctly. Have you checked for any signs of oil sludge? That can mess with the VANOS solenoids.

Thanks for the quick reply! Oil sludge is an interesting point. I haven't specifically checked for it, but I do keep up with regular oil changes. Where exactly should I be looking for this sludge? Is it something easily visible, or does it require a deeper inspection?

Well, with my BMW, the mechanic found it when they removed the VANOS unit. It wasn't immediately visible just by looking at the engine. Given your symptoms and the potential VANOS issue, I'd recommend getting it checked out by a professional. I paid around 250€ for the repair, but it solved the problem.

Thanks so much for the advice. I'll get it checked out by a mechanic soon. It's good to know what to potentially expect. A defect in one of the camshaft solenoid valves caused the issue. The repair cost was 250€ as predicted. Really appreciate your help!