G Klasse diesel throttle issue

I had something similar happen on my G Klasse. Rough idling and the fuel economy tanked. I'd check the throttle body itself. Sometimes they get gunked up and the throttle position sensor throws a fit. Might be worth a look before you start replacing parts. Did the diagnostic tool give you a specific code?

Thanks for the quick response! The diagnostic did give a specific code indicating a problem with the throttle valve. I understand what you're saying about the throttle body. Is it easy enough to clean, or is it better to just replace the entire throttle valve assembly? Any experience with that?

Cleaning it might buy you some time, but if the diagnostic is already pointing to a faulty throttle valve, replacement is probably the way to go. If the valve itself is defective, no amount of cleaning will fix it. I'd suggest taking it to a trusted workshop to get a proper diagnosis and repair.

Appreciate the advice. I took it to the workshop, and it turned out to be a defective accelerator pedal module, as suspected. Replacing it sorted out the issue. The total cost was around 205€. Thanks again for pointing me in the right direction!