I’m not sure I know what you mean by “turns all the way to the left”— you mean that you’re using Pixy with a pan/tilt mechanism and the pan/tilt turns all the way to the left?
I’m guessing— it sounds like you are trying to power the Pixy and the pan/tilt servos through the Arduino cable. This has a tendency not to work because the Arduino cable has fairly low current carrying ability and will drop the voltage, especially if your Arduino is being powered by USB.
Try this instead:
Try to power Pixy through the unregulated power connector and have Pixy power the Arduino through the cable, that is, if you want to power the pan/tilt servos from Pixy. There’s more information here:
http://cmucam.org/projects/cmucam5/wiki/Powering_Pixy