Loraine (Howard) I had two different machines that kept running the way you describe. One was a 1950's New Home that the grandkids were using when it just kept on going!@ They won't touch it now, they think it is possessed. The other one is my Jem Platinum (a new machine). Both times there was something in the foot pedal that got stuck with the machine running. My DH took the foot pedals apart and fixed the problem. The Janome Platinum is known for that problem. I have other friends with that machine that have had the same run away problem.
Nancy