Could I have an injector problem?

2001 MAZDA MILLENIA
15,500 MILES
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POPPABRAND
  • MEMBER
  • 1 POST
The engine codes read P0140 and P0303.
I have already replaced the plugs, wires, distributor and rotor. Additionally all the back plugs are black (1, 3 & 5 with #3 the worst). The engine runs rough and has a definite backfire. Could this possibly be an injector? Or could the o2 sensor cause such an obvious misfire?
Jan 15, 2012 at 12:30 PM
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FIXITMR
  • ✓Experienced Mechanic
  • 9,989 POSTS
rear cylinder bank is running rich apparently.
Jan 15, 2012 at 2:24 PM
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