Land Rover Repair: disco 1 idling, mass air sensor, t4 test

Question
I have purchased a 1996 disco, which starts, runs and drives seemingly very well. No oil burning, smooth running etc. My problem is that the car will not idle at less than 1200 rpm. Ihave cleaned the mass air sensor, potentiometer, throttle position control and cannot find an air leak on the intake system or vaccuum system.
Do you have any suggestions?
Thanyou   Tony.

Answer
If the car were in our shop we would connect the Land Rover t4 test system and watch all the live data on the engine screen while this was happening.  That should tell the tale. Without a tool like that, you are just guessing and that can waste a huge amount of time.  I encourage you to seek a shop with proper tools and skills, because otherwise you can just chase your tail forever, there are so many possibilities