I have a torro riding mower that when started with the choke it runs when i push the choke down it's almost as if the choke is staying open as well when I try and move forward my engine will just die on me could this be a spark plug issue or possibly a filter issue, I cleaned out the fuel and air filters but that didn't seem to help very much. At most i can get the mower to run for approximately 2 min and then it shuts down, also if someone was to put mixed fuel in it could this also cause issues.