Another issue could be your battery. Some users don't realize that if the "C" rating does not support the current draw then the battery voltage tends to drop. Once it reaches the "drop-off" the ESC will stop the engine. Changing the ESC from say a 25 amp to a 40 amp will not cure the problem. But, saygoing from a 15C to a 20 C with the same voltage and "mah" will most likely cure the problem.