I previously mentioned that the car sometimes was hard to start after it was warm well it seemed ok until today when I went for a decent run and on arrival it started to miss-fire a little bit. It seemed to be when I went to rev it, the engine would momentarily die then pick up again each time. After turning it off it was very difficult to start and almost ran the battery down. When it did start it was the same, Missing when revved and there was a bit of black smoke from the exhaust? I disconnected the battery for an hour and after that it was fine again. Set off home and on arriving home it was running rough again. Any ideas from those in the know what this could be?