Originally Posted by
rcboy1
Not to be an a$$, but 7.2V means Nimh

What electronics do you have in the car? sounds like the bec isn't enough...
Too early, no coffee, not paying attention.
Meh 7.2 or 7.4 whats the Diff :P
As for the OP....
Could really be anything, cold solder joint, dodgey motor/speedy/esc connection, dodgey Battery.
Quick and easy way? Got a friend? Or a Local RC store?
Get them to test your battery in one of there cars and vice versa, least then you will know whether its your battery or your car.