Should o2s always switch even when trims are turned off?
I'm trying to diagnose some o2 issues without affecting drivability.

 

They will switch if you are somewhere around stoich,
just on the pulse-wise imbalance and variation. Far from
stoich they will just stay pegged one way or the other.
That's the trims' job, to pull it close enough to center
that you get switching behavior.

 

I have a wideband. And lately the o2 sensors have been going nuts. P1133/53 is what people turn off.

My problem is when I turned it off the o2 sensors would periodically peg at 0, maxing trims to +25%. Since the codes were off it wouldn't fail into open loop.

If I turn off trims I see 1.0 lambda +/- .2 across the board with the wideband.

Tried replacing o2 sensors but it didn't help.

 

Heater and switching codes are meant to inform you
that trimming is likely going south. They are the canary
in the coal mine.

When I had long tubes I ended up turning off LTFTs,
biasing things a little toward the rich side in open loop
and letting the open loop STFT option do the work.
These always start from zero, so you don't end up way
in the weeds, and pulling it to center from rich is pretty
benign (economy and emissions aside - will not ping,
at least).

I think I left it that way after putting the shorties on,
having found no evident downsides to it.
and just letting the STFTs

 

You think I'll be alright with LTFTs off? I've been running like this for months so i guess i've been fine without them. I just don't know why this happened. I've had long tubes for years and just this year o2 sensors last about a month or two before they stop switching.

 

In my book the only place LTFTs save your *** is when
you have a progressive lean error creep (like, say, a
greasy MAF). STFTs starting at zero every time you
step into a new trim cell (FTC) leave you uncorrected
for a little while until they can swing the mixture. So
if you -need- that help, too bad (this is why I biased
things a hair rich). But on the plus side they will not
remember any bullshit from yesterday. You can turn
on open loop STFTs and keep the benefits of trimming
at cruise (anywhere AFR=stoich, STFTs will engage)
and just lose the LTFTs if this appeals to you. I have
found no downside myself.

Another thing you may want to try, is realigning the
FTC boundaries so that (a) more cells are in play (the
F-bodies waste about half of them) and (b) try to
segregate the low-gas-flow regions where heaters
are necessary and insufficient into one trim cell plus
the idle-specific ones; your idle and off-idle may
still be shat upon, but maybe you can at least get
the street and highway rolling operation to clean
itself up.

 

I'll look into that.

I still have to solve the problem of o2s flatlining like they are doing though. When the exhaust flow is low it makes sense, but it would sometimes do it randomly on long road trips. Trims shoot up to 25% on one bank, car starts misfiring. I pull over, get the laptop out, turn trims off. Everything runs fine after that.

STFTs use o2 sensors as well right?