You're welcome. Just a suggestion, but i would look into replacing the radio and receiver. Those are known for having issues, and for losing signal and causing the car to take off. I'm not sure where you are located, but, i would look for a DumboRC with the X6FG receiver...
I have had that radio and receiver on a few HSP cars i bought used, so as soon as i saw the radio, it clicked. I currently have basically the same car he does, set up for on road, with a Porsche body, and an old HSP FM radio setup.
If that is the ESC i think it is (actually been awhile since i seen that HSP blue one), the set button is on the ESC itself (circled in black). More than likely, as already stated, the radio and receiver need to be bound together again. That is the TSD radio and receiver, and the manual for it...