ORIGINAL: flyinwalenda

After you check and set the throttle calibration, if it is constantly stuttering regardless of throttle position then the motor is only running on 2-phase and not 3-phase meaning you probably have a bad connection on one of the three wires coming off the ESC or the motor or there is an internal problem with the ESC or motor
If the connections are all good then try the ESC on another motor and try another esc on this motor to determine which is at fault.
If you correct the connection issue and the motor now runs at full throttle but stutters at low to mid throttle then it is probably the ESC not being able to communicate properly with the responses from the motor. You can try changing the timing from low to mid or high and that may lessen the stuttering and/or you can adjust the start-up from normal to soft start and that may lessen it also.
If you have another ESC (any brushless esc ) you can test with the motor I'll bet the stuttering goes away as these plush esc's seem to have/create the stuttering problem. If you have a different motor , try it with this esc and see if it stutters or not.