Land Rover Repair: engine runs rough, mass air meter, engine management computer

Question
I own a 2004 Discovery se , A few days ago it started running rough. It starts fine, and doesn't surge. I thought it might be a bad spark plug so I replaced them with no change. Could it be the oxygen sensor? Spark plug wires?

Answer
The car could have a mass air meter problem, bad ignition coils, failing wires . . .any number of possibilities.  I suggest you find a shop that can connect to the engine management computer and look at stored fault codes and the data stream.  That's always the next step with these new computerized engine management systems.