'02 3.0 Tribute - 2 new ex. Manifolds & new 3rd cat - New EGR & PCV - all (6) New coils / plugs - all (4) New O2es - Confirmed no vacuum leaks - 85,XXX miles

All recent work re: front cat that puked into downstream cat = limp mode = towed home

I've done a good deal more work than above, but a case "while I'm in there" and gen. maint. to hopefully 're-bulletproof' the wife's pet SUV. And important to note there have been NO CODES since all this work. So, running in the blind with the issues below.

I have a very unusual issue and no info found on here or general search. From dead cold the (brand new) Bank 2 O2 sensor takes over 1 minute to move from 0.0, and then only to peg on 0.01 for the next 1 1/2 minutes. Now this in contrast to the Bank 1 sensor that nearly IMMEDIATELY begins and continues cycling consistently from 0.1 to 0.9 and back. If I don't touch the pedal the Bank 2 will gradually increase its + & - range over the next few minutes from ~0.08 to 0.20, then to cycle 0.10 to 0.35, but it will take over a total 5 minutes from starting for the Bank 2 to move the FULL range and as responsively as Bank 1 from 0.10 to 0.90.

I've recorded the same thing 3 times, but if I hit the gas along the way then it seems to speed up this 'slow wake-up' process to full range readings by a minute or two. The more important question for me is why such stark difference in readings for the two banks, both having brand new sensors - AND brand new ex. manifolds.

I should mention I went and ordered and installed a 'replacement brand new' brand new sensor in Bank 2 as I though the other was defective. $35 'wasted' I guess, but at least one less mystery.

Additional operating details: 60# FP, Starts up fine and idles to 750 quickly, but first couple minutes a slight tiny intermittent choppy idle until the second O2 starts reading a range other than just pegged in the 0.01 - 0.06 area. Once warmed up, then perfect idle and perfect acceleration. All this is not keeping my wife from using the little spud again, just using it more confidently. Any leads on the weird reading patterns?

Full disclosure - I'll be posting this in the Mazda group as well, and share any feedback.

 

Since we need to start someplace, what if you switched the oxygen sensors from where they are now to the opposite banks and see what you get.
Of course I always ask where you purchased the oxygen sensors because if not Motorcraft, could be "foreign made" and a lot of that stuff is defective right out of the box.

 

Thinking the same, and I got all DENSO sensors. Listed by a big online parts house as OEM for the Tribute, and an Amer. Co. IINM. But in all fairness all the originals were Motorcraft so I would have replaced in kind if I had known sooner.

I initially thought of swapping, but when ordering new ones it actually listed different no.s for the front and rear banks. I really wondered about why that could be. I used the leftover 'old' original Bank 1 upper sensor hoping the diff. no. was just the (much longer) pigtail compared the the rear bank, but when starting after I installed it there was no (as in blank) reading on the app at all. For 3 minutes. So, very confused and then simply swapped back to the new sensor again.

Something is confusing me though. Since these are 4-wire sensors that's supposed to indicate heated units. I would have thought the gradually rising readings of the rear sensor was behaving as expected as temps heat up. And then that the front Bank 1 sensor was the one operating too soon by immediately jumping to reading full range even cold.

I just wish it wouldn't start and run so well considering the sensors are acting so differently. I keep reading to learn more about how O2es work.

 

There should be no difference between the oxygen sensors for the 2 that go on to the exhaust manifolds.There could be different reasons for the readings you are getting, but I would suggest you verify the heaters for both front sensors are getting power and ground to the heaters in the sensors.Suggest you use a multimeter to do the testing.
Some folks have managed to rig up a load close to the oxygen sensor heater load to verify it is capable of working. IF all is well there, you will need to determine just why the readings are fluctuating so much. Best to take one thing at a time and once you prove the heaters and circuits are working correctly, you may or may not need to go further, hard to say at this point.

The sensor that goes after the last converter is different and usually takes a little longer to "lite up" begin functioning.

What are you using to get the o2 readings?
If the tool will provide other data, like data stream, could you provide those readings, thanks.

 

I'm using VEEPEAK OBDCheck BLE+ and OBD Fusion on Android. It displays only a single Bank 1 and Bank 2 on the dash, so of course presuming those are the uppers.

Apologies, dam near 3 weeks since reply. I've been tracking and accumulating 'trending' behavior to make some sense of operation. The thing I'm lacking now has been any more legit symptoms of anything amiss - the dam thing is running like a champ again, likely at least in small part to replacing the entire exhaust from cats thru resonator (Y-pipe was fine, but just now ordered the resonator today - the cast bolt flange has heat-eroded and rusted to the point it's so thin it 'bends' at the ends and won't seal the gasket. It's leaking water and going phtt phtt phtt and guaranteed will NOT pass inspection in June).

Note that the currently installed Bank 2 sensor is the second one I purchased brand new. On that first one I had backprobed the leads and used a MAPP torch to heat it but kept getting the reading 0.0. When installing the second new one I was more patient and waited after starting and that's when it finally registered its first 0.01 after almost 2 minutes. From that I'm judging it's not the sensors but the computer,

I may be using the software wrong but attempting to data-stream the sensors all I keep getting is to the effect that, "the vehicle does not provide or support that parameter." The vehicle runs great, quick start, high idle 1,500 settles back to 850, smooth fire - no miss. One note is even though I know regular idle is 750 it stays at 850 forever (past 2 minutes) until I tap it and only then it settles down lower. I did not think there was any mech. kickdown on these throttle bodies anymore. Acceleration is impressive and runs smooth through range.

Note: when idling cold and I tap the pedal there's a faint momentary beginnings of a 'pre-ignition detonation' lag before revs pick up - never happens in gear, and can't replicate it when warmed in neutral. Just interesting.

O2 readings always the same from cold start:
-------------------------------Bank 1 -------------------------------------------------------------- Bank 2
0-1 1/2 minutes ---------Immediate readings, 09-.60 constant full oscillations---------------------------.00
2-3 1/2 min.------------------ .20-.95 constant full oscillations -------------------------------------- .01-.15 constant full oscillating (sluggish pace v. Bank 1)
4 minutes -------------------- same ------------------------------------------------------------- ..20-.95 constant full oscillating (somewhat slower pace v. Bank 1)

As I mentioned in my first post if I increase idle during the first minute I can get initial readings sooner and speed up this 'slow wake-up' process to full range readings by a minute or two. And on the road the Bank 2 will often settles to around .5X-.7X during a pull while Bank 1 is still ranging in a slightly wider but slowed oscillating speed itself. There's steep grades where I live and it pulls hills great with quick kickdown and fast response hi-revs. I've run it enough cycles to get 'Ready for Emissions Testing', and there's no codes.


I noted your comment about the lower O2 being slower to wake up, but more than anything wondering if Bank 1 is behaving normal with its immediate readings since I assumed a 'heated' O2 is supposed to 'warm up' pretty much like the Bank 2 is acting. And of course I would have thought fuel trims would be consistent enough that once equilibrium is established then the readings would be relatively stable. Having both sensors constantly bouncing across their full range and so quickly after warm-up to boot is perplexing. That should be getting into Too Much Information for anyone, but just more intel for any further insights.

An interesting recent development is the wife's sister is interested in buying this one when our new Tucson shows up (May-June est. per dealer). The near-approaching $1,000 in parts I've stuck in it recently has been paying forward for all the years it's been gliding along with no issues. And since it's in just good shape overall (she drives like a *****) I'm just optimizing the $4,500-$5,550 current Kelly Blue Book for it. And there's numerous of the same year for sale online with almost twice the miles and not as clean looking listed for up to $6,000. Crazy times.
I wouldn't try to get those numbers from the SisIL, but good to know it could be going to family.