2004 Nissan Hardbody misfiring and black smoke

Hi. At first the truck didn't want to start early in the morning but will start later in the day. After two days it did not start at all.It was cranking but won't start.when you turn the key to the on position,the engine management light was flikkering.After a few days it started again.It idles normal when cold but when the engine is warm(not overheating) the truck misses,engine vibrates and black smoke comes from the tail pipe.Could you please help me.