What part of the ignition, if it gets wet, needs to be dried out before it start

What is your question?

When it rains heavily, it'll come up with "service emission system " on the dash and it'll go away when it dries out. It rained a lot yesterday and it would not fire. Actually it fired once, didn't even get to idle speed and died right away. It turns over strong, I just had a tune up 2 months ago, new battery a year and a half ago, I've had it for 2 years, has about 190000 miles.The body and cowling have rust and cracks that leak water everywhere so i know that once that gets dried out, it will start and I can take precautions to prevent this again. Thank you for your time and help. Dale

What makes this problem better or worse?

rain