I have a 1.0L 16V Nissan Micra 12 years old. Just recently on a few occasions when the car has been left over night and is cold and possibly damp the car doesn't start and you have to keep pressing the accelerator until it eventually fires up and starts to run you get a bit of black smoke come out the exhaust as it starts up. Once running the car runs like a dream and drives fine. It only has this problem in the mornings. Any ideas? I am thinking it may be spark plugs as they have not been changed for a while at least 16 months.