z31 o2 sensor voltages

[rsfire]

Hello, so I just got Nistune in my 86T. The car runs but too rich under light load, it's in the 12 AFR range on my wideband while cruising with light load. I took a datalog and noticed that while the engine is still warming up, my o2 sensor voltage jumps back and forth between 0.05 and and 2.55V till it's warm, then pretty much rest of the time it reads 2.55V no matter the rpm, load, ect.

Oh and to add, when the car is still warming up, for the couple minutes(still in open loop probably?) it runs mid 14s to 15s AFR, then once operating temps are normal it drops down to the 12 AFR range and stays that way.

So it seems like o2 sensor voltage is way out of parameters right? Maybe it's causing my rich cruising. I have two random thoughts here, for one, the 86T uses the resistance type o2 sensor correct? So could it even display it's readings in Nistune since nistune shows it in voltage? I'm wondering if my o2 sensor is not toasted, maybe Nistune doesn't read that type and that's why it displays weird numbers.

And second, I know I can disable o2 sensing to turn off closed loop. Is that feasible to actually run it like that long term? Or is it accurate or gets better gas mileage to get o2 sensor all figured out?

If anyone wants I can send my datalog to you to help out, just let me know. Thanks in advance!!

[raddy]

looks like factory o2 sensor doesnt work correctly anymore....replace it or bin it and tune whole map for open loop, very easy with your ecu...

[rsfire]

Ok thanks, I'll research how to tune it open loop

[Matt]

Depends on ECU:
http://www.redz31.net/pages/fuel.html

Never seen the O2 sensor go that high (2.55) however. Something doesnt seem right with the sensor if its doing that

[rsfire]

Yep, I have an 86 non turbo ecu, so both turbo and non turbo are the titania. Ok good to know, must be a shot o2 sensor then. Though it seems to run much more normal ratios cruising since I turned off o2 sensing in nistune. But cruising and under boost has AFRs kind of all over the place.
After I let off the throttle from boost should my AFRs still be sitting in the 11s for a few seconds, then sometimes going back to normal high 14s, or mid 13s? It just kind of seems all over but I'm not sure what normal should look like. I'll need to find some other people's logs or something.

And playing back my logs I'll watch which cell it's supposed to be on and it's on the correct cell but my wideband reads up to 3 or 4 AFRs different. Let me know if I need to clarify that.

[rsfire]

Oh and just for the heck of it, I'll attach my last data log incase someone is really feeling helpful haha. I did a 3rd and 4th gear pull then caught up to traffic and was cruising around 55-60ish until I end the datalog. And I know my speed doesn't show, my speed sensor to the ecu must be out. I'm supposed to have another one in by tomorrow.

[Matt]

Yeah that log doesnt look too flash

AFRs are going to 22:1 on the wideband. Please to an open air recalibration of the wideband just to eliminate any bad readings

During those times the RPMs go from 2000 to 1000... injection time is increasing but AFRs going lean? Cant figure that out. would like to see your maps too and injector/MAF used

[rsfire]

Yeah it's all over the place.

I have an AEM wideband so I'm not too sure if it can be recalibrated, I know it says all over that it never needs to be, but i'll need to keep searching to see if there is a way. I'm not sure if you meant that or do one of the tests to make sure its in normal operating parameters. I can try that a bit later to be sure.

And that's weird but I just double checked, my AFRs never go more lean than 17.89 on that log from what I can see. Anyway, I'll attach my map, injectors are stock ones from either an 84 or 85 300zx turbo, the seller wasn't sure. And my MAF is stock one. Though it's little plug is drilled out to expose the variable resistor to lean or richen it up. I wonder if it's messed it up.