I changed my batteries. While running the car I lose control both steering and throttle. I put it on a box with all wheels off the ground and had no issues with controlling it, but when the front wheels would touch the box I lose control again. Then I propped it up on its back wheels and had no issues again! To sum it up, if the front wheels are on the ground the cars response goes in and out! This is really the only way I can explain it
What servos, receiver and transmitter are you using, and what hump pack?
Servos can act weird when the power level is too low, you say everything is charged.
It could be bad transmitter or receiver, is it Traxxass? I hear they have issues like this caused by the transmitter, but its a cheap fix/replacement.
Or
It Could be a Bad servo is causing an issue with high resistance inside the steering servo causing too much of an amp draw, and it becomes unstable, and pulling too much juice to let the throttle operate properly, it starts acting like it has low power.
I would test the steering servo, if you or a friend don't have any, go to a LSH, they should have a servo lying around. If it still acts up, try both the steering and throttle servo, still acting up, get them to hook up a receive, still acting up, its your Transmitter....