Need help of all of you geniuses...

[primerprincess]

Well, last summer my 95 240sx with stock KA engine started acting up. I was driving down the road and it just shut off--no sputter or indicator lights. After I would let it sit and seemingly cool down for about an hour, it would run again and then do the same thing. It took me 2 hours to get 15 miles. Brought it home and ran a scan--knock sensor came up bad (which I heard can be thrown off by other issues) and I replaced it. Also replaced spark plugs and wires, water pump, thermostat, coolant temp sensor and got a new distributor thinking that it might be the sensor inside, but now the car won't even start at all (which is likely the fault of the fellow who put it in, which we can remedy). My main problem is the shutting off. I really need to get this thing in top shape in the next 3 weeks so any ideas at all would be an amazing help. Thanks so much guys!!