Possible Causes

WARNING: This page is about a different car, the 2003 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

Possible causes are:

Fuel pump malfunction
Fuel return hose clogged
Misfire
PCM malfunction
PCV valve malfunction
Pressure regulator malfunction
Purge solenoid valve hoses improper connection
Purge solenoid valve malfunction
Right or left front HO2S deterioration
Right or left front HO2S heater malfunction