First guess......battery. Is it the one that came with it? Probably a NiCd, and shot. What does the label say? Do you have a reputable hobby store near by? Buy a 7.2 volt, 6 cell, NiMh pack with a Tamiya plug. Somewhere in the 15-1800 mAh range. And a decent charger. If it's still a slug, there may be other issues. Start with the battery.