I was checking out an A/C problem and had to start and stop the engine a number of times, the engine was not cold. I had to start and stop the engine a bunch of times and it does run rich anyway at idle.
I took it out and when I would get into the throttle it would buck and fall on it's face along with a huge trail of black smoke out the rear.
Could this be a fouled/almost fouled pair of trailing plugs?

 

yea it may be fouled plugs. take them out and clean them if they look f-uped leading more imp than trailng fwiw