Peugeot 807 fuel consumption issue

I had a similar issue with my 807, though I can't remember the exact mileage. The symptoms sound very familiar. Have you checked the cable and plug connections to the fuel injectors? A defective connection there can cause all sorts of problems with the injection system.

Thanks for the tip! I haven't looked at the injector connections specifically. Where exactly should I be looking, and what am I looking for? Is it obvious, or do I need special tools to check them?

The injector connections are located directly on top of the engine, where the fuel injectors are. You are looking for any obvious signs of damage – corrosion, loose wires, or cracked plugs. While you might be able to visually inspect them, a proper diagnosis often requires specialized tools to test the electrical signals. If you are not comfortable working on the fuel system, I would highly recommend taking it to a workshop, they will quickly diagnose the problem.

You were spot on! I took it to a mechanic, and it turned out to be a faulty plug connection to one of the injectors. They cleaned it all up and replaced a dodgy section of cable. Cost me 95€, but the car is running perfectly again! Fuel consumption is back to normal, power is restored, and no more smoke. Thanks a million for pointing me in the right direction!