Katia, The problem with my Jazz 2 was that the factory didn't set the tensions properly. The technician who worked on my machine said it was way off. After he worked on it, things seemed to be OK. What is really odd is that before the technician worked on the machine, I could go to maximum tension, it would still lash. Now it does FMQ at a setting about #5, but I have to go pretty slowly.
I get the feeling that to do quilting with a machine, it really needs to be one that is deliberately built for the task. But apparently, most domestic machines can accomplish the task as long as you are patient finding the proper tension, and taking your time with the quilting.
In another thread I mentioned that even a machine that says it can automatically adjust its own tension for FMQ, doesn't mean it can. I had to adjust a computerized machine manually, as automatic just would not work.
Good luck on finding a machine that is right for you.