G Klasse Diesel Engine Issue

Sounds familiar. I had a similar issue on my G Klasse. Check engine light, felt like I was towing a boat anchor, and the gas mileage tanked. Is it throwing any specific error codes related to the manifold pressure sensor? It is like your engine is not getting the memo about how much air is coming in.

Sorry, I forgot the error codes. The diagnostic tool indicates error code P0105, which corresponds to a malfunction in the manifold pressure sensor circuit. Given this, would you still suspect a vacuum leak or a faulty pressure sensor as the primary cause?

P0105 definitely points to the manifold pressure sensor. A vacuum leak can mess things up, but that code is pretty specific. If you're not comfortable poking around, I'd suggest taking it to a workshop. They can test the sensor and the vacuum lines to pinpoint the problem. Could save you time and money. I ended up paying around 235€ for the repair, parts and labor included.

I took the vehicle to a mechanic, and the manifold pressure sensor was indeed defective. The sensor was replaced, and the vacuum lines were inspected for leaks. The total repair cost was 235€. The engine performance has been restored, and the check engine light is no longer illuminated. Thanks again for your assistance.