1399 plus a few 300's misfire codes

[aarons mom]

my 99 accord ex suddenly started throwing misfire codes. It has been raining very heavy here. I also have a 1456 that I can not find. Is it possible that moisture is getting in my tank and fouling my fuel? When I add Heet and wait a bit, I run fine. Today I dried out the around the filler neck (yes there was water inside the door) and duct taped the fuel door shut. We will see what tomorrow brings. Could it be as simple as water in my gas? I have been reading about distributor problems related to misfire codes. I guess best case is water in my gas, worst case, tired motor. 197,000/mi. well maintained car. Am I at the end of my life?