Do not worry about the knock sensor. For the misfire, can you check the total resistance of the spark plug cables including the distributor cover? If the resistance is too high your spark will be weak or inconsistent.
Check their total resistance with an ohm-meter. From the connector to the internal post in the distributor cover.
Cyl 1 6.5K ohm max
Cyl 2 10.0K ohm max
Cyl 3 8.5K ohm max
Cyl 4 12.5k ohm max
Cyl 5 8.5k phm max
Cyl 6 11.0k ohm max
If they are over those max values or too close, replace with a new set of wires and a new distributor cap and rotor. Use prestolite brand. That is one of the original brands used by Nissan on these engines. I bought my current set at http://www.partsgeek.com for about $66.00.
If the resistance is way bellow the limits, you could have an injector problem. I would run injector cleaner first, use one that is safe for oxygen sensors.
Lastly, as a worst case, you could have a wiring problem to the injector or a damaged computer output to the cylinder 5 injector.
- This reply was modified 10 months ago by prgonzalez.