Lack of power, intermittent stumbling, codes.

[WestGA]

Stumbling and hesistation issues. Occasional bucking. Code 111 KOEO which is great, but I'm receiving a Code 172 KOER. I recently cleared a Code 157 when I replaced my MAF sensor. I have new Motorcraft plugs and wires and a new fuel filter from when I did a tune-up. Engine takes a few seconds to start up when cold, idles kind of rough, and when it reaches operating temperature, engine will intermittently idle down to approx 500 RPM and stumble. When warm, taking off from a stop at idle, it will lose power and stumble, unable to gain any power to move. During this stumbling, there is a strong fuel odor. 172 is for an O2 sensor, I believe. Where is a good place to start troubleshooting? I certainly don't want to throw money in parts at my truck without further investigation.

 

[WestGA]

I'm gathering that when I perform the KOEO, 111 means everything checks out. For KOER, I'm receiving a hard fault code 172 which is Oxygen sensor not switching – system is or was lean – Single, Right or Rear HO2S – Fuel control.

I'm seeing info pointing to possible causes including unmetered air being drawn in anywhere past the MAFs, a possible fuel pressure or injector issue, exhaust leak between the heads and the sensor, or possibly even a bad sensor.

Another thing I've just though of is that when I replaced my MAF sensor, I didn't leave the battery unplugged long enough to reset. The MAF fault is definately stored in memory still because it's flashed after my KOEO 111 code and the separator pulse.

I'm going to disconnect the battery for a minimum of fifteen minutes and then reconnect and test drive to see if there is a difference. While the battery is disconnected, I'm going to check the plug and harness going to the O2 sensor to rule out that issue. I did have transmission work done recently so it may be a possibility that the sensor/plug/harness was affected.

How does that sound? Am I going in the right direction with this?

 

[SenorNoob]

Just one thing. Unless you have a leak somewhere, you shouldn't be able to smell fuel.