bd0nalds0n

I think I have some disagreement between my new WB02 sensor and my existing NB02 sensor. When I try to sharktune, once I switch back to the NB02 sensor, the car runs a lot richer (as measured by the WB02 sensor). Like, idling in the 10s and 11s. FWIW, my NB02 gauge mounted in the a-pillar shows this as just a little bit lean.

The WB02 sensor is brand new, and I free-air calibrated it last night to 20.2% (or really close), so I have reason to believe it's accurate. I updated my LM-1 to use the scales that John specifies in the ST2 manual.

The NB02 sensor used by the LH is only a couple years old. I purchased a universal model and wired it into my old Bosch connector using butt connectors. The universal Bosch NB02 sensors are $60; it's $150 if you want the model with the proper connector.

Anybody know if the Bosch NB02 sensors are identical except for the connector? I hate to be a cheapass, but a $90 difference isn't exactly immaterial in percentage terms. It's also a PITA to thread the connector through the underside of the car--easier to leave the existing one attached, and splice in a new sensor. That is, assuming it works identically.

Any reason to believe that if I purchase a new universal NB02 sensor and replace the splices using my old connector, that I won't get an accurate reading?

When replacing the NBo2 sensor, does the LH do any kind of free air calibration, or is there any kind of special procedure to make sure it calibrates before putting it in the bung? Or do you just plug and go?

Car is back together and running, but the tune sort of sucks. I see why people say "you'll have 20 hours into it before you know it." I'm taking a couple steps back and making sure everything is close to new and identical to eliminate possible artifacts that would contribte to inconsistencies.

Mongo

I am using universal O2 sensor Bosch #15726 (now supersceded to #15735) and have never had problems with the 3-wire universal. Readings are the same I believe and I have never had to do a free-air calibration on a narrow band sensor. I didn't think you had to in the first place.

Somehow, if your readings are that far off, something got fouled. If your O2 sensor's wiring that is spliced in on the underside of the car got wet, maybe something happened to it? This happened to me last year and I had to buy another one.


I am wondering also if your Wideband O2 sensor lost its accuracy too. I have heard of this happen more than once. However since you said it's new, we can rule that one out.

dprantl

There is no difference between a universal nbO2 and the 928 one except for the length of the cable and connector at the end. And you were still suckered because a mustang O2 sensor is under $40 and you can easily get the other side of the connector at the Ford dealer or a junkyard.

I would check the wiring splice on the nbO2. Then I would take out the wbO2 and do a free-air calibration again. Make sure you are outside away from any exhaust fumes.

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

hacker-pschorr

Did you solder the connections on the narrow band O2 sensor? If you did, that might be your problem. You are not supposed to solder any part of the O2 sensor connection.

In fact, the more I read bout the issues with "non-clean room" soldering, the less I am grabbing the soldering iron. Once you have a professional grade crimper with the proper die sets, you will never solder again.

From Clarks Garage:

Mongo

Hacker, he said he spliced them. I think he used the splicers that are in those universal O2 kits where you insert the lead, then twist the cap to tighten it into the splice.

I bet somehow the connection got wet. I had to wrap mine up in electrical tape to prevent moisture damage again.

hacker-pschorr

The word "splicing" doesn't mean any specific method of connecting wires.

Either way, it's a good information to add to any O2 sensor thread for anyone not aware of that information.

Mongo

I also didn't know soldering would foul connections to the oxygen sensor also. I assumed it's just a simple wire with current traveling through it. Very informative!

jcorenman

Our GT wouldn't idle at all with AFR in the 10-11 range (flaky MAF), just died. So I am suspecting that the WBO2 is lying.

Do you have cats? If that AFR is correct, the exhaust would be stinky with gas smell without cats.

Are you sure the free-air cal was done correctly?

Cheers, Jim

bd0nalds0n

For what it's worth, I did mention that the splice was made using butt connectors. I didn't tape it up to prevent moisture.

I'm going to get a new one today and use the hardware they include. Then I'll wrap that with the self-sealing silicone tape.

dprantl

FYI if you are going to get a new nbO2, here's the info on the '91 mustang V8 Bosch O2 sensor:

http://www.uscarpartsdirect.com/1991...en_sensor.html

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

S4ordie

Per Hacker's post of Clark's Garage:

I would suspect this advice would apply to any silicone based product near or on the connection.

John Speake

Hi JIm,
The alternative to modifying the LM-1 Analog 2 (WB) output law is to change the O2 sensor law that the ST expects (modify in the Options/WBO2 law menu in ST).

bd0nalds0n

I changed the LM1 to the correct voltage as specified by john--0 volts at 9 AFR, 5 volts at 19AFR.

I reset the LM-1 calibration using the software, turned on the LM1 to get the "heater open" message, turned it off, attached the WB02, turned on the LM1, got the warmup message, then the calibration message, then pushed the calibration button. When it was done, holding the o2 sensor, I got 20.2 AFR (or 20 point something) which is supposed to be the "right" amount of oxygen. After that, I powered down the unit and installed the wb02 sensor in the bung.

And it's plenty stinky, even with cats...

When I autotune the idle, everything goes to -128 (even using "custom" 45lb injectors rather than 42, which I'm running). When I do that, the NB gauge on my A pillar goes really lean and the car idles quite roughly. If I then lengthen the pulse width at idle, the idle smooths out some, the NB gauge starts to creep towards less lean, but the LM1 is showing somewhere in the 11s.

I would concur that somewhere I'm not getting readings that are in agreement with one another. I figured that since the WB02 sensor is new, and free air calibrates to where it should as interpreted by the LM1, that a new NBo2 sensor was the next best place to start.

Not to open another can of worms, but what are the effects of a miscalibrated MAF? I wouldn't expect that to cause different readings between the NB and the WB, but it may be another source of inaccuracy.

dprantl

Another quick test you can do is connect the nbO2 emulation from the LM-1 to the car and see if the readings match up to the wbO2.

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

Mongo

Is this also the way the Sharktuner can work on the car? I don't have one, but remember reading that a wideband sensor can be used with a narrow band emulator (from the LC-1) and the ST interprets the signal to the LH.