I wouldn't mess with replacing the o2 sensor until you know for sure it's bad. Get someone's multimeter/voltmeter and test your o2 sensor first. It could save you a ton of headaches, and a lot of money.

The other thing that could be happening would be an injector stuck open. This just happened to a friend of mine on his Hyundai. His car uses Low-Impedence injectors just like Hondas do. You could pull your spark plugs and examine them to determine what's going on in the combustion chambers. Another free test.