It sounds like a tension problem to me. I suggest that you rethread your machine and put in new bobbin. Then try your free motion quilting on a small quilt sandwich made out of scraps to see how the stitches look. That being said, I find monofilament thread very picky to work with. Sometimes machines just need to be serviced because the timing is off or some such thing. Good luck solving your problem.

Usually, top tension is reduced a bit for monofiliment. Don't know how "auto" handles that but you might check it. Best to work on a sample sandwich a bit first.
Linda

I had pretty good results (the one time I did this) by using the monofilament in the top only and cotton thread in the bobbin. I loosened the tension on the top as well. Fran is right on--use a quilt sandwich to see how things are working together.

Sharon C.

I've had similar problems. One thing that I've heard is do NOT drop the feed dogs. They will "bump" against the fabric but not really pull it anywhere 'cause there's nothing pressing it down assuming you're using the darning foot. Anyhow, apparently on some machines this helps with tension.

Your issue definitely sounds like a tension problem, but I have also found that a bobbin not wound just so was the issue, believe it or not. When quilting -- free motion or straight w/ walking foot, I've taken to starting with a test sandwich of fabric and batting to see if it's behaving, and then reaching my hand under often to feel to make sure there aren't a bunch of loops on the back.

After doing all those other things and still having trouble, I have sometimes found that the problem disappeared after I cleaned in and all around the bobbin case and blew some air in the upper works where the upper thread passes through (Can't get at that part easily to clean it manually in my machine.)

I've had to adjust bobbin tension too with monofilament. If you hold the thread coming out of the bobbin case, drop it, and it should fall about 3 inches and stop.

I ... quilted at a very fast speed.

I'm not sure exactly what this means, but I suspect that this could be the problem, or at least part of it.

If the needle is going up and down very fast, you still want the quilt sandwich to move very slowly, so that it is making regular size stitches. Big stitches, even if there are just a few here and there, mean the quilt sandwich is moving too quickly. You need to learn to move the fabric at a steady rate, no matter the direction or tightness or looseness of the curves.

Practice on small scraps. You must have a light touch. Just your fingertips. If you pull the sandwich, you'll cause the stitches on the back side to pull.

When I first started to free motion quilt, I gripped the sandwich tightly, and dragged it back and forth under the needle. The fabric moved rather quickly. I liked the way it looked on the front side, but the back was a disaster! My stitches pulled so badly that I could see a lot of the top thread on the back side. And thread didn't even stay where the needle had gone through, but pulled to the inside of every curve.

Since then, I have slowed waaaaay down. But the needle still moves relatively fast. And I have learned to hold the fabric gently. I did a lot of practice with scraps. I put different colors of thread in the top vs. the bobbin. And I used muslin so I could see every stitch, until I got the hang of it.

Some computerized machines have a feature that regulates the maximum speed. You can press down on the gas pedal as hard as you want, and it tops out at a pre-set speed. This is very useful for learning the steady speed aspect of free motion quilting.

I have seen the Bernina Stitch Regulator on TV and in person. Seems nice, but if you can just learn to move the sandwich at a steady rate all by yourself, you don't need anything that fancy.

I agree with Maryliz - that's exactly what happened when I started to do free motion. Are you getting most of your pulled and distorted understitches on the curves? It could be because you are moving the fabric too fast. When I slowed down the problem went away.
Clara

Maryliz, this is exactly what I must be doing wrong. I will practice, practice, and practice. Thanks everyone!!

Practice, practice, practice. Good luck!