Originally Posted by glennshute
Have u tried adjusting the mixture with the mixture screw on the engine ecu.Put the car on an emissions tester n turn the screw till the emissions get back 2 where they sud be.
I wouldn't do that IF you know that the car was running well enough previously to pass an MOT before the car was laid up and nothing has been changed since.
Sounds like it could be either the water temp sensor at the rear passenger side of the head, or the wiring to it.