Hello! I have a 2004 Mazda rx8 6spd. The car was running good then all of a sudden it was hesitating/stumbling/backfiring and would not idle.

I've read through countless threads on here. I've replaced:
Plugs
Wires
Coils
Purge valve
cleaned the ssv (which is still bad I think)
Cleaned the maf, then replaced it
New crankshaft position sensor
and new CATALYTIC converter.

Now since it started running bad I can smell a lot of fuel, I took the plugs out again and noticed the front rotor plugs were wet with fuel and the rear plugs were a nice dry brown.

I've tried the brake pedal 20 pumps and removing the room fuse but no change. I haven't done a compression test because the nearest Mazda service center is over an hour away.

Only check engine light is p0031 o2 sensor.

 

Sounds like a misbehaving or miswired injector on rotor 1. You've replaced everything else. Just make sure the coils are correctly connected to the harness and to the correct front rotor spark plugs. And the O2 sensor sounds like damage to its heater circuit, so that should be a straightforward replacement.

 

Have you done a ghetto compression test by cranking it with the plugs out to make sure you can at least hear 3 pulses? Things like SSV wont affect idle that only comes into play higher up in the revs. How hard is it to start?

 

I have not done a ghetto pressure test, but today I had it started and all of a sudden it sounded bad, like when you roll your R's constantly with your voice.

Also, afterwards I took the fuel rail and injectors out. Is there a way to text them to see if they are good?

 

Have you checked to make sure that the rotor is actually firing? I would put a timing gun lead on the leading and trailing wire to see that the plugs are getting juice.