Make sure the feed dogs are engaged and the pressure foot pressure is set at approx. 47. Re-thread the top and the bobbin - in fact, switch the bobbin thread to another one just to try. Also try a different piece of fabric. If all that doesn't help plus the other suggestions above, then it just might be time for a 'spa' treatment for you 440. Mine just had one as her Christmas gift from me! She sews like a champ now.