I will probably be the bummer here. I have a singer 403a (1951). No matter what I tried, I could not FMQ on this machine. There was some sort of tension issue. I had tried every variation of settings, I did the equivalent of putting the feed dogs down (my throat plate goes up), but alas to no avail. The husband bought me a new machine, and I had no issues whatsoever. So After you try all the above suggestions (hundreds of times), just realize it may not be an operator error, and a limitation of the machine.