I recently, about 3 weeks ago, replaced the battery in my 2003 Tribute. Now I am getting poor gas mileage and when I cold start it, the rpms go up beyond 3000 and slowly go back down to the normal cold start rpms. I took it to the mazda dealer and the tech said that the computer had to 'relearn' my driving habits. Computers don't take 3 weeks of daily driving to 'relearn' my driving. And what about when it was new?? It didn't have to learn anything then...

 

Yeah, that "relearn" thing sounds like a crock. Could you possibly knocked something loose when changing the battery? Maybe a sensor that is causing the computer to react falsely?

Maybe try pulling codes from the computer at a parts store that has a free one to use?