2003 Mazda 6 Rough Running

I recently had a similar issue with my Mazda. Mine is a V6, but the issue was due to a bad coil. Not sure if it's the same w/ a 4 cyl, but the 6 cyl versions have an individual coil for each cylinder. It didn't quit completely, but was firing intermittently, which made it run rough. Pretty expensive fix on the 6 cyl because they are hard to get to so there is a lot of labor. Then you have to decide to just change the bad one, or change them all while they are in there.
But the issue will surely come up during a diagnostic.

Mine too is doing the same thing I have replaced 3 coil packs now I would recommend if you could change them all at once do it it is very difficult to keep tearing the car apart to change them because after u fix the one that is bad it seems a couple weeks later another one goes bad