Discovery 300tdi auto 1997 ,fly by wire electronic acelerator pedal.
When driving and i stop and put gear selector into park or nuetral the engine revs upto 1800 revs, sometimes i can lift the peddle and then the revs drop down to 850 the check engine light comes on and then the revs go back up to 1200,and the light stays on,if i then very very gentle touch the peddle the revs go back to normal 850 tick over and the engine check light goes out. Any ideas please ..

If yer stick yer head under the dash yer'll be able t see the top o the accelerator pedal, the bit wi wires on is the potentiometer an thats worr'll be bustid ! probleeey ?

Failed crank sensor,high idle is due to the ecu defaulting to the needle lift sensor on No4 injector which is a less stable signal and non-exsistent on overrun.Stick it on Testbook to confirm,at least one code should log and you can confirm on live data that the rpm signals read different values.If you are lucky it might just be a bad connection.

Thanks for your answers ,ive not checked either as yet, now she wont start easily when cold ,and winds over 2or 3 times when warm, is it all the same fault.