I have a Proform 830QT treadmill. It runs, but it will stop without warning?

Check your electronic choke to see if it is overheating . It may have burned out which is evidenced by the coils showing a burned area. These can be found for about 44 dollars (treadmill doctor.com)plus shipping . That is what happened to mine and it was doing the same thing. It is nothing more than a cheaply built imitation transformer in my book. Hope this will help.

steve o
August 2009