What is wrong if the car will not stay running?

I have a 1984 Honda Accord that does well most days. About every 2 to 4 days it will start fine, then for a day or 2 it will not start, good battery, have replaced coil, plugs, wires, distributor, cap, rotor, fuel pump, and had to replace floats in carb. Starter fluid does not help, most of the time it happens after car has set over night, mainly when it is 45f or less, I put a 100w light under hood at night and that seems to help. I have a 1984 Honda Accord that does well most days. About every 2 to 4 days it will start fine, then for a day or 2 it will not start, good battery, have replaced coil, plugs, wires, distributor, cap, rotor, fuel pump, and had to replace floats in carb. Starter fluid does not help, most of the time it happens after car has set over night, mainly when it is 45f or less, I put a 100w light under hood at night and that seems to help.