Land Rover Repair: discovery 1993 fuel injected 3.5l v8, coolant temperature sensor, mass air meter

Question
When I drive and put my accelarator down to go faster and the engine revs up, it spews out black smoke out the exhaust, I was told that this is possibly over fuelling. Do I look at replacing my coolant temperature sensor that goes to the ecu or fuel injectors or what? Please help, I love my land rover but it just drinks the fuel, only 400 km on a tank of fuel, thanks.

Answer
My first guess would be a fuel pressur eproblem.  Next I'd suggest you get the workshop manual and go through the tests they describe to check the sensors.  The coolant sensor is a possibility but fuel pressure or a mass air meter are more likely I  think