Check engine light comes on and engine starts runing rough right before it dies.This has happened twice on two consecutive days after I have mowed a hour or so. Both times the engine was idealing because I was off the mower. First in started and ran rough for a second and then leveled out, but the second time was a different story. It would not start, so I check the code and it gave me a 31. I let the engine cool for around 15-20 minutes and tried it again. It started rough and cleared up quickly. Finished mowing with no problems. Any ideas on what may be going on. Engine is new.