Did you change your needle? A small burr or nick will really affect your tension. I'd also check my bobbin case for any nicks or burrs. The Janome has a wick hole under the bobbin case which sometimes dries out causing the bobbin case to rattle and jump and sometimes the needle makes contact with it causing a nick. Nowhere in the manual does it tell you to oil it there. Inspect the case, oil the wick hole and change your needle. Also make sure that your feed dogs are dropping all the way down to disengage and allow you to FM quilt. (Don't even ask how I know all of this) Needless to say I was a very unhappy FM quilter for a long time and I had a dealer who wouldn't believe me that it was the machine and not operator error!