2003 Mazda Tribute

Engine Performance problem
2003 Mazda Tribute 6 cyl Two Wheel Drive Automatic 85,000 miles

Front cat recently replaced; old one broke up, plugged up exhaust. Ran fine for a week, then ran rough lost power; DTC- " random misfires" Got tune up, several new coils, including cyl 4 and 5.

A week later, " check engine" light on again; it runs fine, but codes say misfires on cyl 4 and 5 and front cat is bad.

Had codes cleared, drove about 200 mi, and same error codes come up again - misfires on 4 and 5, front cat bad. Meantime, it runs great! What's the problem" Could PCM itself be bad?
March 25, 2010.

Check compression and injector for no.4 and 5

P0300 Random misfires normally point to vacuum leaks and contaminated fuel

Mar 25, 2010.