I'm learning to FMQ and I have had that happen a couple of times. One time there was a tiny piece of thread loose in the bobbin case...I cleaned everything out. Another time it looked that way especially when I made a curve or corner. I think at that time I was move the fabric too fast. FMQ is definitely a learning process. Good luck!

How long have you had your machine? If it's from a sewing machine shop, maybe you could take the sample and let them give you suggestions.

I had this same problem this week, and in the past. Had been FMQing a lot and this just happened. So, rethread bobbin and top and then get the muslin out and check the stitch again - I played with the top tension a teeny bit and it went away. Now, to re-do those 8 blocks I took out Monday! (when I'm done here, that is).

First thing I was taught at a Pfaff convention:

When there are loops on the top, the is a problem in the bottom. When there are loops on the bottom, there is a problem with the top.

This is 'mostly' true. I agree with everyone, raise the presser foot, rethread the machine top and bottom. Make sure the bobbin is spinning in the correct direction and has 'clicked' into the little tension guide.

However, I was also taught to change the needle every 8 hours of sewing and sometimes more often when quilting a quilt with polyester batting.

Let us know how it turns out.

Adjust your top tension, check your needle, make sure the threads are compatible with each other. I use 40w on the top and 50w-60w in the bobbin, but there are other combinations you can try.

I use the Bobbin Genies in all my bobbins. For machine quilting and piecing. Take out the spring thing in the bobbin case and put in the washer. The spring thing will go right back in if you ever want it too. I don't think the washers work with plastic bobbins or drop in bobbins? Anyone know?

That's what I would say. Right now I am in a quilting class (8 weeks) to learn the finer aspects of quilting. We use the Machine Quilting Made Easy by Maurine Noble
http://www.amazon.com/Machine-Quilti.../dp/1564770745

One of the first exercises she has you do is test the tension of your machine. You take a sample sandwich and mark lines horizontally at 1" increments. Then you start at line 1 and set your tension to 1. Select your stitch and sew at that tension until you get to line 2. Change the tension to 2 and sew to line 3. and so on. This REALLy helps understanding your machine and finding out at which settings she sews best.

You can try this method using different stitches, different threads, different battings, etc. Takes the fear out of the tension issue.

Good luck.

It looks like your upper tension is too tight. I agree with the others. Re-thread, check the bobbin and try on a sample piece of fabric(s) the same thickness as your quilt.

I have a Pfaff Quilt Expression, plastic bobbins, no springs. I use the washers for everything, even piecing. Sometimes when I make tight curves and stitch fast the stitching tends to web. Tightening the top tension helps.

maybe you were going to fast