PSI-FX4

I have been suspecting a Catalytic Converter issue slowly developing over the last 10,000 miles. While I do NOT have a CEL, I have been doing some driving and logging my 02 Sensor voltage with my scan tool.

What I have noticed is a bit puzzling. Now, my understanding is that the rear O2 sensors should stay fairly steady with some slight variation. What is happening on mine is the following.
This is slowly accelerating from a redlight to highway speeds, and setting cruise.

Bank 1 Sensor 2 voltage ranges from .195-.890 - levels off at .720-.750, the bounces wildly for a second, then back to level.
Bank 2 Sensor 2 voltage ranges from .460-.830 - levels off at .730-.740

Should Bank 1 be bouncing around like that? To me, that indicates a degraded converter doesn't it? But the switching isn't enough to trip a code.

What side is Bank 1? Passenger? Anyone have any input, or am I over analyzing it?

PSI-FX4

I've noticed while idling my long term fuel trim is -5.5% on both banks. Short term on bank 1 was typically +1.5-2% and bank two was -1.5-2%.
While driving at hwy speeds on cruise, my long term fuel trims changed a bit. Bank 2 was typically -7.5 or -8% while my bank 1 was typically -6 or -6.5%

So.... What I'm understanding (someone please chime in) is that the first O2 sensors (which my scan tool will not pick up for some reason) is reading a slightly rich condition on both banks at idle, thus calling for negative fuel adjustment. This can possibly be concluded by the bank two sensor readings as well from slightly elevated levels (.735-.750volts) post converter. I'm assuming that the voltage should be .450volts in the second bank sensors as well.
While driving, the long term fuel trim went more negative.

Any ideas/suggestions?

maplelakeduckslayer

The o2s will drive you crazy...I tried figuring them out for months. Wideband o2s function differently than regular o2 sensors so make sure you research the correct one

PSI-FX4

Forgot to mention also, that I drove my wife's 2015 Explorer Sport (same engine obviously) in the same conditions and both long term and short term fuel trims were ZERO for an average (might have changed .8-1.5% for just a few seconds then went back to zero). And rear O2 sensors read about .1-.2 volts lower. From my understanding the rear O2 sensors are narrow band, an the front O2 sensors are wide band, which my Harbor Freight scan tool cannot read. Not 100% on that, but at least that's what I'm understanding.
It's compensating for something, which is too much fuel. Can't figure out what or why. This I feel is the reason I'm having a rising oil level also.

Possible leaking injector maybe?

PSI-FX4

Update. Done a KAM (keep alive memory) reset last night, and done the same driving as before. Long term fuel trim settled at -2.3% at idle (short term was basically zero on bank 2, and positive 2% on bank 1), and while driving I saw no change from previous. Bank 2 was -7% and Bank 1 was -5% LTFT at hwy speeds. Now, this is normally acceptable, but was what still has me thrown for a loop is that at times the short term fuel trims will bounce down into the -10-12% range which puts a total fuel trim down into the negative mid/high teens. From my understanding it takes a 20% or greater change to trigger a CEL.

At idle, on the passenger side, I can hear a very, very faint hiss coming from somewhere. I went all over all the vacuum lines that I can see and came up negative. I don't really like the idea of spraying a flammable liquid all over a hot engine in order to find a vacuum leak, but a lot of people recommend it. It's possible all this is a result of a small vacuum leak (indicted by the positive 2% on bank 1 at idle)?

I do have an 87 octane tow tune from KEM (been on the truck since 25k miles). Surely this wouldn't be built into the tune?? Every tuner I know normally strives for 0% long term fuel trim adjustment (at least with what experience I have anyways).

Again, I have a comparison vehicle with my Wife's 2015 Explorer Sport. Something is going on, and I'm determined to track it down. Next step I guess is installing the stock tune and re-test to see if I get similar results.

torchred04

You ever think it might be the 02 sensor starting to go? I had my bank 1 sensor fail at 105,000kms and I bet it was starting long before that based on my crap mileage and truck felt more sluggish.

Changed the 02 sensor and got a livernois catted downpipe and truck feels really good again and the bank 1 02 sensor code is gone.

I would think 02 is failing before the cat.

PSI-FX4

It's possible Bank 1 Sensor 1 is slowly starting to go, but is still working "within spec". I'll see if I can't find a way to read that sensor to see what it is doing.

kruman

My truck has almost the same symptoms as yours. I have tried to log my O2 sensor readings with torque pro but never had a baseline to compare them to. Please keep us updated on your findings.

PSI-FX4

Okay... got some more information for the ones that might actually be interested.
I have not loaded the factory tune to verify, but after a day of driving, the long term fuel trim as settled to where it was previously (-5 or -6%).
I was able to update my Harbor Freight scan tool and after the KAM reset I can now read 47 sensors instead of 32 previously.I can now see the first sensors (wide band) and watch their current change, as well as equivalent ratios. equivalent ratios are particularly handy as a ratio less than one shows a rich reading, and likewise a ratio greater than one indicates a lean reading. It should oscillate back and forth from 1 to achieve the perfect air/fuel mixture. As previously stated, wideband O2 sensors are different and indicate lean/rich via current either positive or negative, compared to a regular O2 sensor which is strictly voltage. I've done some tests, and my preliminary diagnostics was that my Bank 1 Sensor 1 was working correctly, but slower to respond to changes (WOT blip test) than the Bank 2 Sensor 1. After B1S1 responded to the WOT blip, it took a much longer time to settle back out. It's unfortunate that I cannot see both of the graphs side by side (can only view one at a time). So, in order for me to confirm, I'm going to have to have to get some data logging software (via a PC I suppose) and compare side by side.

maplelakeduckslayer

This is what my o2's looked like when I replaced them. Sooted up one is drivers side, and that's the one that failed. When I started a thread on it everyone said the sooty one was normal, the other one being clean was problematic. Well since replacing them, now both sides are sooty like that. Have you pulled yours out at all? I've still been trying to find out if they should be sooty or relatively clean. To me it seems if it was getting all sooty like that and it failed, it shouldn't look like that.

And also, what is causing it to get sooty. I have been curious if a clogged cat would limit exhaust flow and cause the sensors to get sooty like that causing poor readings. I dunno I still have a lot to try and figure out.