Originally got a 420, Cat problem than got a 131 misfire read out and than a 154 no O2 reading on the driver side cyc 2,4,6 and 8 side.

Pulled plugs and 2,4,6 and 8 were very black but no oil just black soot. 1,3 5 and 7 were perfect, replaced plugs made sure plug wires were OK and seperated. Motor still missed under loan, than O2 code showed up, 154, changed both oxygen sensors on passenger side, Car still misses, but no code is being throw so the plugs, cleaning of plug wires and making sure they were not cross firing and adding two new o2s to the right bank did nothing. The car misses when you are lugging the motor, the car has an unusual exhaust order. With no codes showing but a bad miss present can the opta spark be bad with no codes.??????? An y one got any ideas what to do next, like replace cat converter??????????????

 

Are you getting spark from the passenger side?

 

Looks like the right bank is running rich. The computer adusts each bank independently from each other using one Oxygen sensor on each side (on '96 and later cars, there's actually two on each side, but the second one is just for the cat converter test). Something is causing the computer to incorrectly think that the right bank is lean and it's dumping extra fuel into it causing it to run rich.

By the way, 2,4,6,8 are the passenger side (typically referred to as bank 2)

If there's literally no O2 reading on the passenger side (bank 2) it sounds like either a bad O2 sensor, or damage to the wiring harness. Take a look at the sensor wiring to make sure nothing is cut or melted(under the car, the sensor in FRONT of the cat converter, screwed in to the top of the pipe just at the bend).

If you're getting a proper signal from the bank 2 sensor, it could be a bad injector. Do all of the plugs on that bank look basically the same?

As mentioned above, definitely check the spark. A bad wire/plug would cause a misfire as well as cause the computer to think it's running lean since you're not burning all of the oxygen in that bank.

Other possibilities would be an exhaust leak before the O2 sensor, but you'd probably hear that.

 

Mark thank you and all for the input every plug on 2,4,6 and 8 look exactly the same the are black with heavy soot. May be I need to change the o2s on the driver side based on what you have stated as well. I had what I thought was some kind of exhaust leak when I bought the car on the side in question in fact I drove with a 420 for a long time thinging the after market mufflers was throwing the code but no miss at that time. It is missing at an idel and over 1400 it smooths out if it would only throw me code again I could do something.