I was mowing the other day and my cub cadet just shut off, not like it ran out of gas it was like the key was turned off. I checked fuel, replaced fuel filter and sprayed carb cleaner. It will turn over, it is getting fuel and spark it will start firing once every few seconds never reaching full idle. can sometimes get it to reach full idle but it generally dies quickly after. I have never seen anything like it, cause it does fire and run but wont fire regularly to reach full speed. Any ideas?