I've been having issues with flex fuel for a while. Everyone keeps telling me the O2 sensors are the problem. I logged them but am not sure what exactly I am looking at. They all seem pretty close to their partner. The rears have some differences but I'm not sure if it's an issue or not. Could anyone take a look and give me some idea of what is going on?

 

What code/s are setting?
Need to go by their Ford Descriptions to begin the understanding of the issue..
Good luck.

 

rear sensors do not chance fueling, they just report catalyst efficiency to the best of my knowledge so wouldnt worry about those

 

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As or at least 18 up, the rears do have some influence on fueling as well as cat efficiency monitoring when the PCM does a separate test of the cats.
More advanced from early design.
The sensor design is even different, now.
Good luck.

 

No codes. It does this thing where it thinks I'm running E85 when I run 87 through it.

 

On another note, all the videos I have seen where the O2 sensors are being looked at everyone talks about watching them switch high to low. The PID I used to log were the only ones I could find for the upstream sensors unless I'm blind. They show mA instead of volts. Is that why they don't look like they are switching high and low? The rears look like they're switching properly.

 

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These are totally different deign. 5 wire A/F ratio detectors right at the exhaust for instant feedback and fuel correction to the MAP Sensors.
Can't go by the old type for how they work.
If your concerned by the LTFT shifts positive, it's all normal.
Afterall, E85 puts a lot of Oxygen in the exhaust the Sensors detect as too Lean and cause fuel injection to Richen up, as it needs to do.
This will shift the fuel tables positive.
If you have no codes, there is no issue.
The Tables will not set code until that shift is 25% or more in either direction from zero reference point on either or both banks.
Your chasing a non-issue, otherwise.
If you need more info, reference Ford's OBDII Overview Doc on how they work.
Good luck.

 

Front sensors are wideband sensors. They have a more instantaneous reaction. They should graph a fairly straight line around zero mA at a stready RPM with small throttle changes. Milliamps higher than zero is lean and milliamps lower than zero is rich. If you give quite a bit of throttle or quickly decel you will see some spikes in the graph but should quickly return to close to zero. Under a hard acceleration I believe you should see the graph go rich.

 

That is the problem in a nutshell. The truck, running 87, calculates the ethanol level to be E85. Shifting the fuel trims and timing accordingly. That causes the truck to have issues with serious pinging under any kind of load. The ECM never sets a trouble code. It sounds like the heads are going to come apart while driving, but still no code. I would think the knock sensors would see that and do something but nope. I have to reset the ECM to get the ETH calculation to come back to normal. I'm working with 5 star tuning currently to get a tune made to disable the flex fuel option for my truck.

The whole point to looking in to this to begin with is everyone that I tell about the fuel issue I have with my truck tells me my O2 sensors are bad. Everyone that sees the chart and logs tells me the O2 sensors are fine. I just wanted to make sure I'm not crazy and there is nothing electrically wrong with the truck before I get the tune finalized.

 

I had already described how the flex fuel is handed when Oxygen content changes in the exhaust.
There is no disabling that whole series of actions.
Have there been any changes to the program or engine you have not mentioned?
Is the fuel pressure low? What is it running fully warmed up?
When changing fuels with greatly different Oxygen content, the program cannot change instantly but over time as the Ox Sensors continue to detect the fuel fed, stabilizes to the >average< of the mix in the fuel tank.
There are specs for how much refueling and at what levels in the tank, per how the PCM Program handles it.
Its all documented in the OBDII Overview on the subject.
Normally with these engines, Octane numbers are not used in this way and cause some confusion.
in fuels, the Octane does not come from one source but an average of all the additives and base fuel mixed together. There are as many as 10 additives in many fuels.
Ox Sensors only deal with the Ox detected, not any separate sources in the fuel. This is the basis of them being wide band.
The Ping and Knock is a problem that has some cause that must be found.
Is it a lean condition from lack of fuel, Air leak, wrong sensors in place etc.?
The Ping and Knock is the fuel is to lean, to much air, Ignition timing to far advanced etc.
A Lean condition causes the combustion speed to spread >peak to fast before or to near top dead center< where the Piston/ Rod / Crank can't move fast enough in the space. The Piston, Rod & Crank throw are to close in straight alignment. This rings the Heads, Block, Piston and Crank, like hitting them with a hammer. Cylinder Pressure peaks to soon in a small space.
Other possibilities are Detonation from hot spots already in place that ignite the mix without spark plug help.
Take a look at the ignition timing action, what does it do? Maybe the knock sensor is not working.
Diagnostics is the key by looking at all possible sources that can cause it.
Good luck.