1997 dodge ram 5.2 runs rich

Please read the post and comments before commenting. Thanks.
I got a 1997 Dodge Ram 1500 5.2L. It has ran rich ever since I got it in a swap a while back.
I have gotten the problem better after working thru some codes but it still runs rich. After a couple hundred miles it will foul out the plugs.
I have a fairly basic scan tool. It says bank one sensor 1 short term fuel trim. This number will be negative to positive 4%. Bank 1 sensor 2 short term fuel trim is always 98%. Both O2 sensors have voltage moving around. Anyway here’s the new parts it has gotten.
Plugs wires cap rotor
IAC sensor
TPS sensor
Front and rear O2 sensors
MAP sensor
Thanks for any thoughts

Has anyone checked the fuel pressure?

The problem might be with the in-tank fuel injector pressure regulator.



Not yet. I’m trying to borrow a electronic reader for the injectors and try to see what’s going on with the fuel system side

Are you certain the engine is running rich? Perhaps there was a fault for rich mixture, what does the computer show for long term fuel trim?

Oil fouled spark plugs are a more common problem and may cause a misfire, operating with a misfire will cause a rich mixture and foul the other spark plugs.

The smell of unburnt fuel at the back of the truck is strong. Plugs are new but with a few hundred miles they will be black and fouled out. It had a code for one of the 02 sensors stating a lean condition. It hasnt came back up yet since replacing both of them but it’s only gone 10 miles since then. These numbers are at idle. It has a very slight miss. Numbers stay about the same as it warms it to temp
Short term fuel trim bank 1 goes from 4.3% to 8%
Long term fuel trim bank 1 -1.6%
Timing advance cylinder 1 moves from 12 to 18
Absolute throttle position 12.5%
Short term fuel trim bank 1 sensor 1 3%
Short term fuel trim bank 1 sensor 2 99.2%
Calculated load value 4.3%
02 sensor voltage sensor 1 moves from .140 to .800 volts
02 sensor voltage sensor 2 moves from .020 to .800 volts

It sounds like you fixed it. The failing oxygen sensor was sending a lean signal to the PCM causing the computer to enrich the mixture.

After this type of failure the adaptive values should be cleared with a diagnostic scan tool or by disconnecting the battery. If the memory is not cleared the adaptive values will self correct after 10 to 20 minutes of driving.