Engine Question

I have a '99 Nissan Maxima V-6 with 154k on the car.
Just recently I have noticed when I start the car after it has been sitting for a few hours, the car idles over 1 rpm. Then dropps to under 1rpm after the car has been running. This morning I was driving to work and the car started to sputter I was going 65-70mph. When the is stopped at a stop light the car idles rough. What would cause these actions? There is no smoke or leaks. And the check engine light is on.