2003 Nissan Altima Q&A

2003 Nissan Altima Question: what causes miss fires in Altima 2003,also would a defective cat converter cause

coil 1 and 2 have been replaced, codes 042 and 300 keep coming up -
Answer 1
seek diag and est as it could be several issues,a plugged catt would cause misfires and lack of pwr -