What could cause a misfire if the ecu does not throw a code?

Your engine can misfire and a code will not show if:

1 your could be arcing if they are laying across each other

2 the wires are arcing against the engine or other metal object

3 one of your spark plugs is fouled and is not firing the cylinder

4 one of your plug wires doesnt have a good connection with plug or distributor

5 possibly a crack in the distributor cap

6 possibly faulty rotor within distributor cap