I'm fairly new to nitro, but I was having the same problem. It's called a flame-out. I believe, if the mixture is too rich slightly, the carb builds up with fuel while the car is sitting still, then when you apply the gas, it rushes all the fuel into the motor, and it basically suffocates the motor, causing it to stall or "flame" out. Keep high revving the motor a lot before you run to "clean" it out, and maybe lean out your mixture a bit. Like I said, I'm fairly new to nitro, but it sounds like the problem I was having.