My 2001 Corolla literally sounds like it is sucking water in somewhere when it’s raining. When driving through a lot of water, or a puddle (especially on the driver’s side) it looses power and sounds as if something is sputtering water into the engine. All visible hoses seem to be solid, the idle has been a little rough and the two ODBD codes generated since this problem (only ones ever) are P0420 and another for the evaporative emission control system- forgot to write that one down. Been resetting the MIL for a few oil changes now, but the problem seems to be getting worse and gas mileage is slightly lower. Does any have a clue where to start?
This link explains the causes for your code and possible fixes. O2 sensors, catalytic converter or exhaust leak.