P38 R/rover 4.0l Rough Idle & Central Locking

Hi, My Rangie Starts And Idles Fine Until I Engage Drive Or Reverse When The Revs Suddenly Dive And The Engine Vibrates And Runs Very Rough. When Cold It Stalls And Even When Warm Struggles To Pull Away. However On The Move It Runs Smooth And Accelerates As Normal.also The Drivers Door No Longer Locks/opens With The Central Locking But Is Fine With The Key.any Advice Will Be Very Much Appreciated.

On your idle check all vacuum hoses are your ht leads in good condition as well as spark plugs,you could also check your tickover as it sounds low on base level,if you lock passenger door on sill button does drivers door lock as well,if not could be latch wire or linkage fault, if it locks on drivers side key does it lock all other doors and unlock other doors or only drivers door,if it locks all doors fault will be with the solenoid in drivers door, if it does not lock or unlock any other doors first check connectors at the bottom of A post behind panel take screw out of petrol shut off solenoid panel pull bonnet catch and remove trim check connectors are not going green if ok next go to door wiring open door and pull out from car side not door side the rubber tube which holds wiring for door,when rubber is free pull on wires gently car side 2 connectors are in the hole check again for greening and poor connections if still not working im afraid you will have to remove door card and check all the way to the latch and operation at that end,hope this helps tiga.