so RC cars usually receive a 27 or 1 MHtz radio waves some others use IR(infra red) you should check if there are led light's in front of your remote if you dont see any it's probably a radio transmission car, and with adding sensors to it I cant help because the cheap car's usually have a micro chip that analyzes the data for forward, backward ,left ,right, boost and break.
If you still dont manage to understand what is it's communication method post a picture of the remote and car.
I'm hacking a cheap rc car as my first project! The car I have uses an RX TX pair of IC, with the RX in the car (receiver) and the tx in the remote (Transmitter). With this setup, transmission is one way - you can't send a signal from the car.
I removed the rx chip from the circuit board inside the car, and connected the arduino to replace the rx control pins. I programme the arduino, then let it run! The next step is to build sensors in, to control movement.
I think if you want to control the car remotely, you'll have to replace the communication tool with a two-way system, maybe Xbee, but that's beyond me right now....
Is it possibility to just take the transmission and reviving parts of a rc rx tx bundle by this I mean only the antennas and there controlers and connect to arduino for more channels for controle
Why don't you think to build a RC car from scratch instead of hacking it. I can bet it will be better as you can learn a lot and can change to anyway you want.
To build a RC car, you need to have some electric components like a pair of transmitter and receiver (wifi, bluetooth, RF, IR ...), some motors, motor drive circuit, battery, arduino board ... All this goes into the RC car chassis.