Miss, Lean, and Rich

[m202748]

My mom inherited a 1999 Explorer 4X4 4.0 SOHC in a contested probate. It sat for 6 months, and when she finally went to start it, it wouldn't fire. She took it to a shop and they changed the fuel pump. Now it starts, but runs terrible. It will fire on first crank, but idles rough, stalls on decel, and is extremely rough and sluggish under load.

Codes are:
0301 Miss Cylinder 1
0303 Miss Cylinder 3
0304 Miss Cylinder 4
0305 Miss Cylinder 5
0306 Miss Cylinder 6
0171 Lean on Bank 1
0175 Rich on Bank 2

Changed plugs, wires, fuel filter, air filter. MAF looked clean, checked most of the vacuum hoses, and didn't see any cracks or signs of leakage. Pulled ~19inHg of vacuum. I'm leaning toward telling her to sell the truck as-is, unless there is something easy/common that I might be missing. I have very little mechanical skills or tools.

What's next?

 

[2000StreetRod]

O2 connectors crossed

The common cause for one bank to be lean and the other to be rich is when the pre-cat O2 connectors are crossed. The connector or wires for the left bank sensor are connected to the right bank sensor and the wires for the right bank sensor are connected to the left bank sensor. The PCM gets confused because it receives opposite side data.

 

[m202748]

The common cause for one bank to be lean and the other to be rich is when the pre-cat O2 connectors are crossed. The connector or wires for the left bank sensor are connected to the right bank sensor and the wires for the right bank sensor are connected to the left bank sensor. The PCM gets confused because it receives opposite side data.

Thank You for the response.

Would this affect open loop?

Under WOT it still runs rough. I confirmed that it was going into open loop under WOT with my code reader.

 

[2000StreetRod]

open loop

. . . Would this affect open loop?
Under WOT it still runs rough. I confirmed that it was going into open loop under WOT with my code reader.

No, when the PCM is in open loop the fuel trims and O2 sensor outputs are ignored. The air/fuel ratio is based on production tables stored in the PCM.