New to forum here, need some help with this v10 running rich. It is throwing code for both banks running rich. I ran the live feed on my scanner and have found specs listed below ranging

LST ADAP% = (-.1) - (-16)
RST ADAP% = (-.5) - (-18.3)
LLT ADAP% = (-28.5) - (-32.9)
RLT ADAP% = (-23.5) - (-32.9)

I am not to familiar with these 8.3L motors, but am pretty mechanically inclined if someone could possible steer me in a direction of fixing this. I also have a zoomed in shirt clip of the live data at idle after a short drive.

 

Wow, it looks like the LT fuel trim is pulling fuel in a major way.

I would check fuel pressure, and pressure fall-off when you turn the key off. It should hold pressure for at least a few minutes....

How old are your O2 sensors? (front 2) If they were change recently, what brand sensors were installed?

 

I have not check fuel pressures yet, will try and do that today. The O2 sensors are the original sensors, which vehicle has about 85k. I do have two codes popping up which are the abvious rich conditions on both banks, and the other is knock sensor low voltage. Would knock sensor have anything to do with fuel trims? Maybe it thinks the motor is knocking and trying to up the fuel to minimize it?

 

That's possible, usually though, if it sees knock, it just pulls timing advance.

It *might* be that the O2 sensors are just getting old, changing them certainly wouldn't hurt..... (NTK or Denso only please) Of course, there are other things could would cause it to run rich, that won't necessarily set codes as well. (bad map sensor being one of them...) Even something as simple as a vacuum leak.....

 

That all deff makes sense, i greatly appreciate all your help.

is there by chance a quick way to eliminate o2 sensors being the problem, maybe unplugging them to see if it changes anything or stays the same?

I have not been able to get to the truck latley at my other shop so I'm just trying to gather a few diff directions to go with that I can try when I do get a chance to play with it.

It is a little odd, the truck runs fairly well, just very horrible gas mileage. 😒

 

If you unplug the sensors, it'll set codes, and the truck will just run on the tables the PCM has for 'base' maps. (fuel, spark, etc) It won't go into closed loop. (which is when it starts paying attention to the O2 sensor, usually just a couple minutes after startup.) If the truck actually runs better with the sensors unplugged, that's a pretty good indicator that they are bad. If it still runs rich, likely something else is causing it.