My 2007 Ford f650 stop engine light comes on and I lose all response from my gas pedal when I make left hand turns only.

SOURCE: 2001 Ford F650 with 7.2 Cat deisel acceleration problem

Check your TPS Throttle positioning sensor. Sounds like it has a dead spot in it or it is failing. May also be a wiring harness issue or loose connection at TPS too! If its intermittent then it will soon go out completely. It should be located on your fuel pedal. Remove it and check it with an ohm meter. Check resistance all the way thru from 0-100 percent. When it is not working it should do nothing and show no resistance. When it is working the resistance value will increase and or decrease as you turn the sensor.

SOURCE: 2007 Ford Explorer loses power when making left turn in tracking light comes on

if its a constant then check out abs sensor -hub for damage or need of replacement if happens on occasion than its doing what its suppose to and that is to reduce power so as not to cause a roll over or slid of vehicle if the vehicle senses to fast a turn or wheel slide will reduce power (traction control)