I am in the process of redoining a porch. When all said and done the floor height difference will be about 4.5" between the room. Is this "step" okay or is this against most codes.

It's not against code, but it's not considered good practice, which is to either have three steps or no steps. The reason is that, while you and your family will become familiar with the step, visitors, or the elderly, or those with poor eyesight, may not see it, and may in fact fall. The best thing to do is construct a ramp about 4 and a half feet long, if you can't level the two floors. Leveling the floors would be the best thing to do.