Mongo

Brian, how old is your MAF? I just had to replace my MAF because the calibration went completely bye-bye. My MAF was a rebuilt unit (definitely not done by Jon Speake) I got 3 years ago. It failed last week and made the car run really lean and hesitant when applying gas.


Can you swap MAFs with someone just to see if the running characteristics change?

jcorenman

Air is about 20% oxygen, and residual O2 is what the WBO2 is measuring. But that's not the same as an AFR of 20.2. The AFR of air is infinite but the WBO2 electronics limit out at some value, usually in the 18-20 range. So that might simply be the max readout for AFR.

It sounds like the NBO2 sensor is responding to changes in fueling, correct? I don't know how likely it is for a NBO2 sensor to be working but out of calibration. I always thought that the calibration was a result of the zirconium or whatever it is.

What happens if you just let the LH run at idle in closed-loop mode and watch it with ST? Ignore the WBO2 number for a moment, you should see the O2-adjust number somewhere between +/- 20%, and hunting a few percent up and down as the LH teaks fuel. If you see that (irrespective of WBO2 reading) then the NBO2 sensor is behaving rationally, and the LH is able to control fueling within the adjustment range.


If it smells like gas then that's a indication that the mixture is indeed too rich. But I don't know if that is a reliable check with cats.

I think the ST's autotune is looking at the WBO2 sensor, not the NBO2. So this suggests that the WBO2 is lying (reading rich). If it was simply a goofy NBO2 then autotune should be able to dial in the idle mixture and have the WBO2 indicate 14.7 or thereabouts, and idle smoothly.

The fact that it goes to -128 AND the car runs worse says that autotune is going the wrong direction.
And when you add fuel manually, the idle smooths out and the NBO2 is happier. That's all telling me that the NBO2 is behaving rationally. However, fitting a new one is a relatively cheap thign to try.

(I am also skeptical that the NBO2 "breathes" through the wires, but I crimped mine just to be sure. Moisture should not be a problem if you locate the splice under the CE panel where the original disconnect is located... ).

A MAF cal problem causes the LH to inject the wrong amount of fuel. Ours was intermittently reading high, i.e. said airflow was higher than actual, which told LH to inject more fuel, which stalled engine with AFR in the 10-11 range. If it ran long enough to warm up and the LH went closed-loop, then it was fine-- the LH reduced the fuel until the NBO2 was happy.

In any event the WBO2 and NBO2 should agree at 14.7 (and ours did).

The only time I've seen the sensors not agree was recently with changing altitude, and a new free-air cal fixed that.

Tony

are our cars twins or have a pscyhic connection or something?

Im have the same issues now.
I recently(last week) have swapped in another LH unit(and my PEMS) that cured my hot start and hesitation isues but now i cant get the car to idle right...symptoms almost identical to yours!
VERY RICH at idle. Car will quit when coming to a stop at a light..etc.
-128 in idle cells. the O2 sensor shows +20% for a correction when not autotuning. Tweeking the injector sizes i CAN NOT get the correction off 20% (full scale). i dont want to change the injector size either as my WOT is based on 33.8 as a size.
Lm-1 showing one AFR...STer showing another.
i did a free a calibration after the car sat for 4 days (while at work) and it is fine....shows 20.9% O2.
i rechecked the LM-1 look up for the analog ouput...volateg vs AFR etc etc...looks good.

starts fine cold but as it warms up it starts to hunt and will eventually "choke" itself.
When i get some time to devote soley to the car im going to get the car up to temp and just unplug the 02 sensor at idle and see what happens. My Super MAF is fine, it has recently been checked by John. As a quick test, i unplugged it and the car quit right way.
Other than the idle, the car pulls like an animal now.

Good info on the O2 sensors as well, thanks. I have some more things to look into. I have mine "spliced" in as well. Perhaps this is/was the cause for my original hot start and hesitation issues...and not a bad LH?

FYI..this is on an orignal ST ver1. update to work with PEMS
Ill be picking up Ver 2 when a few other fix its get done around the house here.

I personally think it has to do with our 02 sensor(s) the way it looks..sounds..and "smells". Atleast you have cats on!

jcorenman

You can connect the LC-1's narrow-band emulator output to the LH, in place of a separate NBO2 sensor. This lets you replace the factory NBO2 with a WBO2, if you only have one bung. That's independent of the Sharktuner, which would be connected to the LC-1's WBO2 output.

But that brings up a good point: Brian, does the LM-1 display match the wbo2 reading displayed in Sharktuner? If so, then your WB output setup is correct (0-5v = 9-19AFR).

Cheers, Jim

bd0nalds0n

I thought the LM1 is what feeds the ST its data from the WB02? My point is that I would assume the ST says whatever the LM1 says, since the ST gets its feed from the aux out of the LM1.

I'll check it out to make sure. Both the ST and the LM1 have been indicating the car is running rich (which it sure smells like), but the NB gauge reads lean.

When I fatten the idle up to where the NB gauge reads "nice," the LM1 reads really rich, like in the 10s or 11s.

I did change the WB setup on the LM1 to 0 = 9, 5 = 19.

I may go ahead and run the NB emulator to the LH, so at least everything is being fed from the same 02 sensor. That takes at least one variable out of the equation.

Mongo

I would try that and see what happens.

Then, get that new NBO2 sensor and do a recalibration again of the WBO2. Plug everything back in and see if there is any improvement after the new sensor.

danglerb

Would it make any sense to switch bungs between the nb and wb?

Maybe find some other way to check the rich / lean condition?

Tony

eh..in the meantime, just put a small ignitor in your exhaust pipe.
ill post what i find..when i get to it.

jcorenman

Correct, but the LM1's display is directly connected to the WBO2 processor. To get to the ST the AFR first gets converted to an analog 0-5volt signal by the LM1 then sent to the ST, and converted back to a digital AFR number.

There are three places where things can go awry:
The AFR-to-voltage conversion (which is the 9-19 range you set), a ground-reference issue with the analog voltage, and the conversion back to AFR at the ST end (which by default is also set to 9-19 AFR).

If the ST and the LM1 read the same then all those things are fine. That still doesn't tell you whether the NBO2 or WBO2 is lying, just that there isn't a third number floating around...

How is the LM1 grounded?

Cheers, Jim

Mongo

This was something I was worried about when running 2 oxygen sensors. If each one is plugged in on one side of the engine and each bank runs differently, that would probably throw the ratios off too.

I had a friend that ran dual WBO's on a Ferrari Testarossa a long time ago to troubleshoot running issues, hence my question for it at the time if that was really the right thing to do when I had installed my X-pipe. This was also the reason I did mine at the center.

PorKen

Jayzus, just buy the proper sensor, ya cheap boostards. Seriously - crimp connectors? Even if you pay the list price of $150, it's going to last the life of the car.

If you shop around you should find one for around $100. Shop cost is $70 or less for a Bosch 13 048.




To the original problem, if the NB and WB are on different down pipes, perhaps there is a leaky injector, ignition, or other problem on one bank?

dprantl

I don't like paying Bosch $100 for a small length of wire bundle and a plastic connector which costs them $0.20. What's wrong with crimping? If you do it right, it's no different than the crimps on the terminals inside the connector. And nbO2 sensors usually last 60k - 100k miles.

Anyway, if you really want to do it properly, do what I do. Chop off the connector on the car side and crimp (or solder) a mustang V8 connector to the car. Then you can always plug in the $35 sensor without messing with it at all. All our cars here have '91 mustang V8 O2 connectors

Dan
'91 928GT S/C 475hp/460lb.ft

PorKen

Look at the big brain on Dan!

Except, there should be an a-dapta-kit to - plug - into the factory plug, wired to another plug, to use the el-cheapo sensor.




PS: only crimpers crimp on 928 parts.

Mongo

He's right. I've crimped and spliced without any problems with an O2 sensor. Just KEEP IT AWAY FROM WATER.

dprantl

Ken! I never thought of you as a... purist But seriously, the Ford connector is 1000 times better than the 928 one.

Dan
'91 928GT S/C 475hp/460lb.ft