I'm sorry you are having this problem. This type of problem can be from the ignition transformer or the spark plug. Since the spark plug has been replaced, the most likely problem will be the ignition transformer. The ignition kit is # 102482-04. However before replacing this part I strongly recommend having a technician check it, to determine for sure. This can be a difficult product to diagnose even for technicians and when not working properly can be very dangerous. I'm listing a site you can access, to have a tech come out. Here is a link for the website:
Sears Home Services
. Thank you for using Manage My Life.