Here are some ideas that come to mind:
Transmitter battaries low
Make sure any power wires like your battary wires and motor wires are away from your servo wires, antenna, esc wires that plug into reciever, and reciever. Don't mount your reciever on your servo if it is.
Motor may need a rebuild (comm cut, new brushes, cleaning)
Check solder connections and make sure they're not frayed
Did your car work with your dad's power capicitor before? If it never worked with you replacement buy a new replacement from Novak.
If you have a graphite or aluminum chassis keep the antenna wire from touching it (make a hole about an inch from the base of the antenna tube so your antenna enters through there on the tube instead of the bottom so it doesn't touch the chassis)
Your crystal could be damaged so try a different set
Your reciever could be damaged
If your servo is broken it could cause glitching.
Hope some of these ideas help!