Toyota Repair: 1996 Tacoma 2WD, spark plug wires, oxygen sensor

Question
QUESTION: When it rains or has been raining, and the engine is cold, it runs very rough (almost like it's missing a cylinder) until the engine fully warms up.  This only happens when it rains.
ANSWER: Humidity will aggravate an electrical misfire condition, is it a 4cylinder or V-6 engine and is the "check engine" light on?

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QUESTION: The engine is a 4 cylinder.  The check engine light comes on whenever this happens but usually goes off after several days with no rain and the engine runs normally.  When the light comes on it gives me a code for a bad oxygen sensor  in the exhaust which I have had replaced.

Answer
When the engine is running normal without a misfire take a spray bottle filled with water and spray a fine mist on the spark plug wires and see if the engine starts to misfire, if it does replace the spark plugs and the wires, if this was already done and didn't help let me know. The O2 sensor code sets because of the misfire, the sensor was not the problem.