Nissan Repair: 96 nissan xe moisture issue, spark plug wire, moist weather

Question
Nissan 96 xe pickup truck 155k miles, manual tranny, straight 4
2.4l. engine runs rough until warmed upin moist weather or humid weather.   It has sat in very wet weather for a week or so and will not start now.  Cranking is good but it will not fire.  I have had the car tuned up but continue to have the rough running issue in moist weather.  Sometimes it will idle very roughly or stall altogether if it is wet and cold engine all until warmed up.
Once it is warm it runs ok until it has a chance to sit in the wet again.

Answer
Hi Doug -

When the tune up was done, did they replace the dist. cap and rotor?  Special attention the the rubber seal that goes between the cap and distributor. Moisture could be penetrating into the dist. cap. What about the ignition wires?

You say the car is not starting now? Would you be able to do this test:

Pull out a spark plug wire and insert a screwdriver into the boot until it wedges against the terminal inside firmly. Hold the screwdriver shaft about 1/4" away from any metal surface of the engine while a helper tries to start the car (do not touch any metal surface while doing this). There should be a spark jumping between metal surfaces.

Let me know your results -

aloha
calvin