The Car had the air mass potentiometer disconnected by the technician, and I was asked to drive the car to see if the fault reappeared. The fault was much less evident on a run, however during a period of idling at standstill, the idle started to rise, with black smoke coming out of the exhaust. I then reconnected the air mass potentiometer, and disconnected the Electro-hydraulic actuator. The fault manifested itself this time by an intermittent high idle. Difficult hot starts remain with either of these devices disconnected. It is as though the ECU is getting an intermittent signal to go into cold start enrichment, or possibly full open throttle. I am wondering if the throttle switch could be at fault. I am going to clean up the connections on all of the electrical components of the fuel system, to make sure all the contacts are good and free from corrosion etc. The car has a new coolant temperature sensor. Any further suggestions regarding items to check would be most welcome. There is one sensor that I am unable to identify, which is situated in the air intake scoop, at the front of the car. Presumably this is an air temp sensor, and does it send a signal to the ECU? (the car does not have the external temperature gauge in the dashboard fitted.)