ORIGINAL: hugger-4641
I've had the same problem with a couple SC's. Besides what was mentioned above I've also had two other things cause the problem you're having. If using the stock 27mhz radio, the ACT can glitch and cause sputtering or even kill the engine completely, turn the ACT off and see if helps. If using the stock motor, there is a diode soldered between the wire leads on the front of the motor, the connections can get damaged in a nose first crash and also cause sputtering. Otherwise it probably is a battery or antenna issue.
Good thinking about the motor diode. It totally forgot about that.
Another idea, since the stock diode is probably one of the cheapest things on the plane, pick up another one and put it in place. The stock one might be bad.