The following steps will hopefully guide you to make your own RC car controlled by Arduino.
Step 1: Taking Apart RC Car
You need to take apart your RC car and take the IC off the circuit board. You can do this with a pair of pliers, soldering iron or a solder remover.
Step 2: Connect the Arduino to the RC Cars Circuit Board.
Once you have done that you need to get a length of rainbow cord with four wires about 10cm or more and connect a pin for each wire. On the opposite end you need to connect four resisters to each wire again and that will then be soldered on the circuit board where the IC went. You need to locate the forward, reverse, left and right hole on the circuit and that will be where the resisters will be attached. The other end with the pins is how the Arduino will be connected to the car. You also need a wire that connects on the earth on the Cars circuit board which will then go on one of the grounds on the Arduino.
Step 3: Entering the Program
The next step is to plug your Arduino into your computer and enter the program you want. Then you get a 9v battery that will then plug into your Arduino. This will allow you to put figure of 8 codes and others along with adding sensors onto your RC car.
Step 4: Putting It Back Together
Once you have entered the program you want test it on your car. If it works you can put the cover back over your car and drill a hole on the side to allow the rainbow cable to go through and sit the Arduino on top of the car with hot glue.