Old Rover 214 question

[mrskins]

Hi Peeps,
The wifes car has started pulling back while driving as if there is damp in the dist cap. This morning it would not start so I pulled the cap off no probs dry. After a while it started using no throttle with a pop of black smoke, turned the engine off and it did the same again, on the ground where the exhaust kicks out is a patch of black soot so it has to be fuel related. I have a sneaky feeling its a sensor gone but which one??

Thanks

Si