Question about RC Toy Car and Servo Motors

[Ziggy]

I am new to robotics and I have a question: Is it possible to add an extra servo motor onto a micro controller of a toy car? I am building a robot from a RC toy car. Now the movement of robot is done(I moved the front DC motor to the back and both back wheels are now rotating independently, so that the robot can move in 4 directions) . What should i do if i want to add a servo motor onto it?

[jwatte]

Do you have more transmission channels available on your RC receiver?
If so, you can use the unused transmission channels for more servos.

You are mentioning a "micro controller." Is this a processor, like an Arduino? If so, yes, you can likely have the Arduino output the right control signals for an additional servo, and power the servo from the batteries. More servos will lead to proportionally shorter battery life.

[Ziggy]

The controller come with 6 buttons, 4 for 4 directions, and another 2 were used to run both motor in 2 different direction. It's the one like Arduino, but it was frmo the toy car itself so i dont think we can programme it like Arduino right?

[jwatte]

If you don't know how to re-program the MCU, then no, you cannot add more servos to the MCU without replacing the MCU.
If you don't know how to hook into the receiver output, then no, you cannot use the existing remote control to control new servos.

"toy car" is impossibly wide to talk sensibly about, though. A $29 Radio Shack RC special is very different from a $499 kit car that's made of individually replaceable components.
What toy car is it, and did it come with any instructions, and/or is it modular in any way?