Most likley a tuning problem... Bad glow plug is also very likley.
Try changing the carb back to factory settings(if it is the TRX 2.5 engine, read this http://www.traxxas.com/support/troub...buretorpro.htm )

To check the glow plug(thing in middle of engine if you look down from the top), take it out of the engine.

If you have the EZ-Start system:
Look on the bottom of the plug, you should see a coiled wire.
unplug one of the wires going to the ez-start motor.
Make sure the glow plug wire is connected to the glow plug.
Grab the glow plug with some pliers and hold it agains the engine head.
Plug in ez-start controller and press the red button(like you would start the truck)
As you press the button, you should see the coil inside the glow plug turn bright orange.

If you did everything correctly, and the plug did not glow brightly, the glow plug is fouled.

If the plug did glow brightly, it is fine.

If you use a glow ignitor:
Remove the plug.
Connect glow ignitor to the plug
It should glow bright orange

If the plug did not glow brightly, the glow plug is fouled. Or the ignitor battery is dead.

If the plug did glow brightly, it is fine.

Hope that helps, and makes sense.