During wet weather my pthfinder will flood out.

During wet weather my pthfinder will flood out and not run properly. I have checked distrubor cap, spark plugs, brand new tank of gas with heet treament, parked in garage at night, does not have this problems in dry weather. Everytime it is wet outside it will flood itself out and die, it happens before I have a chance to hit a puddle so no water splashed anywhere. Everytime this happens my tach will read 0, any normal time tach works just find.