Hey guys. So i had successfully finished my 5.0 to 5.8 swap in my 1996 f150 e4od. The 5.8 is from a 1996 e150. So im having some issues with these o2 sensor codes. P0171- system lean bank 1, P0174 system lean bank 2, and P0136 o2 circuit bank 1 sensor 2. All sensors are newer and from the 5.0L. Symptoms i seem to have are, harsh start ups, lack of power, seems to run really hot (havent read temp with a scanner yet). Now a few things to wrap up the story, its currently running on 93 octane fuel. The exhaust is a f250 5.8 downpipe. I welded in my own o2 sensor bungs. I have no exhaust leaks around bungs, and manifolds. Any help would be greatly appreciated. Thank you!

 

Running lean will run hot and burn up the engine.
Do you have a y-pipe, cats, muffler and tail pipe all connected?

 

Its just a couple feet of pipe hooked up on both sides of the engine. No cats, mufflers, tailpipes

 

Looks like you may not have the third O2 sensor connected or may be hanging in the air (P0136).

The front two O2 sensors may be too close to atmosphere with only a few feet of pipe connected. Where did you install the O2 bungs on that F250 h-pipe?

 

Front sensors are 2 or 3 inches away from pipe flange that bolts to the manifold. Sensor 2 is plugged in and is screwed into the oem sensor bung that the hpipe cane with

 

Do you have shorty or long tube headers? Where is that in relation to how the factory had the upstream O2 sensors? How are you going to get rid of the downstream code with no converter?

 

oem exhaust manifolds and the bungs are in same position as a oem piping. Maybe millimeter off? and i havent had a cat on this truck. Second time ive gotten code like this. 1st time, i replaced the sensor and everything was fine.

 

The rear/third O2 sensor is used to calculate converter efficiency. With no converter the signal may be skewed, but then again the poor man's MIL eliminator was a spacer to move that third O2 sensor out of the exhaust stream.

The front O2 sensors should be fine based on your response so it makes you wonder if both banks register lean it may be low fuel pressure or a MAF meter problem.

 

With only a couple feet of pipe you might be sensing lean on the O2.
Put more pipe on or mufflers on, see if that makes a diff.