Best confirm its not a spark plug problem (By swapping it with one from another cylinder) Does misfire change cylinder? Also confirm you are getting a spark at each plug lead. Problems here, especially if its been lying are probably to do with the distributor cap.
Plugs always soot up if the car is only run idling from cold.
Had similar symptoms a few times with Micras that have sat idle for a while. I'd go for dirty fuel.
Take the fuel filter off and drain it onto some kitchen roll, fuel will probably be 'rust' coloured.
Best thing to do is take the fuel pump housing out, clean it out thoroughly. Take the fuel pump out and clean the pick up filter (which will probably be caked with rust too)
Next, syphon the fuel out (Best to do it thru the top of the tank as the filler neck has anti syphon flaps), leave the tank to dry out then thoroughly clean all the crap out the tank.
Stick a new fuel filter on and some nice clean fuel.
Misfire and any remaining rust will burn off with use.
If you want to check the injectors are getting power etc. one of each terminal will have an ignition live, the other will have a switching earth from the ECU. You can make sure this is happening by using a noid light (LED with 2 pins) or a testlamp with LEDs. Cant really test with a normal testlamp.
I wouldnt try removing the fuel rail and cranking the engine to make sure each injector is working as you will just end up with petrol everywhere.
If everything else is ok, try swapping the suspect injector to see if the fault changes cylinder too.
Injectors are usually pretty reliable though.
