Mercedes V Klasse rough idle and fuel consumption issue

Sounds like it could be fuel starvation. I had similar issues with my V Klasse. Have you looked to see if the gasoline injectors are clogged? Sometimes it's a misfire, but usually it's a fuel problem.

Thanks for the suggestion. When you say 'checked', do you mean just looking at them, or do I need to do something more to see if they're clogged?

Looking at them won't tell you much. The clog is usually inside. You'll need to get them cleaned or replaced by a professional. I took mine to a shop. They said it was the injectors, and it cost about 500€ to fix. It's best to get it checked out before you assume anything.

Thanks for the help. I got the injection nozzles checked and one was bad, just like I thought, because it was clogged. I had to replace it, and it cost 515€. The car runs great now.