97 2.3 code P0300 (random misfire)

[5speedin2.3]

My 97 has been getting about 200 miles to a tank and I can't figure out why.
First I had cyl 2 misfire(P0302), now its random misfire (P0300).

I took it to my friend yesterday and he hooked it up to his live data scanner. He said the only thing that looks off is the rear o2 sensor is reading 0volts.

Help! I've been chasing this problem for over a year and its starting to get worse.

 

[97ranger xlt]

non functioning 02 sensors would cause bad fuel mileage.

 

[5speedin2.3]

Its the rear sensor. All it does is monitor the catalytic converter.
The upstream sensor works fine.

It being bad doesn't explain the random misfire.
I replaced the plugs and wires last spring hoping this would solve the problem.

 

[BT2413]

What have you done related to better fuel mileage?

 

[5speedin2.3]

Heres a list of the things I've replaced in the past year.
Cam sensor, plugs, wires, MAF, PCM, upstream o2, fuel filter, air filter, DPFE sensor.

In the past three years I replaced the engine and used all new gaskets, low mile engine.

I get the code P1443, but I have all of the evap system unhooked and the line is plugged at the intake. I replaced all of the valves/sensors/hoses and its still there.
I also checked everything for vacuum leaks with carb cleaner and the idle never changed.

 

[BT2413]

I am wondering if you might need the PCM reset or replaced....

 

[5speedin2.3]

The PCM is the exact same number as the original. I've swapped out the two and it has the same issue with both.

 

[mp3deviant721]

Check the ignition coils for good spark.

 

[5speedin2.3]

Check the ignition coils for good spark.

I did with a test light. All eight throw normal arcs.

I even unplugged each coil and drove it. It seems fine on a single coil, but a little down on power.

I sprayed the coils and wires down with water, no arcs.

 

[mp3deviant721]

Is it running rough now? Or does it come and go?

 

[5speedin2.3]

Is it running rough now? Or does it come and go?

It seems to come and go.
The CEL is off right now, but still has the codes in the memory.

I'm going to go buy an o2 sensor Friday and hook it up to see if the PCM is picking it up. If not its getting returned for other parts..

 

[5speedin2.3]

Idk if this helps..
But if I accelerate over 4500rpms while the engine is cold it sputters and wants to stall out.

The truck is also running very rich. The exhaust smells like gas.
It has thrown bank1 too lean before, so I think it might be reading lean and dumping fuel to correct the problem.

 

[mp3deviant721]

What about fuel pressure? Did you check that? A bad regulator can cause all sorts of issues. Or a fuel pump that starting to go out. That bogging out at 4500 rpm makes me think that the engine is not getting enough fuel pressure. So if you haven't checked fuel pressure I'd also check that.