Hydrogen Fuel Cell

I've started to work on a hydrogen fuel cell to put in my vehicle.  I don't have the book, because I don't want to spend $300 for something that may not work!  I have worked over it mentally several times, and I think I have something that will work.  I put a rough draft of one in a car about a year and a half ago, and it turned off my check engine light!  The car didn't have a catalytic converter in it, and was getting a bad reading from the oxygen sensor.  Apparently it started burning clean enough to remove that code.  The only problem that I was having--after about an hour or so, the water was so hot that it was boiling, therefore putting a water vapor into the engine rather than the pure hydrogen and oxygen.  oops!  Well, let's see in a couple of weeks if it works.