Low voltages coming from narrowband O2's

[nickp223]

I logged the averages for the narrow band O2 sensors and most of the voltages are below 600 some as low as 50 and there are none in the 800's to 900's range. My LTFT's are averaging -10 across the board. I have a 99 camaro 4L60E trans with the 3800 engine. Do I need to poSsibly replace the O2 sensors. I can usually smell unburnt gas from the exhaust so I know the car isn't actually running lean. Any help and or suggestions would be great.
Thanks

[KLUG'S SS]

Are they the original O2s that came in the car?

[nickp223]

I am almost certain they are.I know the one after the cat is stuck in there pretty well because I tried removing it Should I look at replacing both the forward ones?

[KLUG'S SS]

I am almost certain they are.I know the one after the cat is stuck in there pretty well because I tried removing it Should I look at replacing both the forward ones?

I definately would! 10 years is a long time on O2 sensors and just because you dont get a code for a bad O2 doesnt mean that they arent worn out and arent switching how they should.

[nickp223]

Alright then. I'll have to use my wideband money to replace them then. But then I should be able to go by those new narrowbands to some degree correct? Until I'm able to invest in a wideband.

[nickp223]

what im wanting to do is correct my long term fuel trims but am afraid to do so and have the car running too lean on me. Im assuming that once these are replaced then i can start to correct the trims using the narrowband to make sure im somewhat in the ballpark of the 12-14 range.

[passingpower]

There is one thing that NBs do very well; measure stoich in closed loop. That's the only thing they can be depended upon, and then, only when fairly new. If your goal is to lock down LTFTs, you won't do it or keep it using old sensors. Bank on that. NBs are made to very tight tolerences, they have one ratio to measure. WB not so much. NBs don't need to be calibrated, WBs do. By the way, how much do you trust that WB calibration?

Short answer, CL tuning trust a new NB. OL tuning use a WB and don't take the calibration for granted.

[KLUG'S SS]

There is one thing that NBs do very well; measure stoich in closed loop. That's the only thing they can be depended upon, and then, only when fairly new. If your goal is to lock down LTFTs, you won't do it or keep it using old sensors. Bank on that. NBs are made to very tight tolerences, they have one ratio to measure. WB not so much. NBs don't need to be calibrated, WBs do. By the way, how much do you trust that WB calibration?

Short answer, CL tuning trust a new NB. OL tuning use a WB and don't take the calibration for granted.

Do you actually believe that a decent wideband isnt accurate?

As eficalibrator (Greg) stated in a different thread not too long ago that GM uses widebands on every engine dyno to build those fueling maps in the first place.

[passingpower]

I'm not making any statements according to what i believe my guts are telling me, I've been reading other posts on this and other sites regarding WB accuracy. Are they inaccurate? No, not as long as they are properly calibrated.

GM has the resources to ensure proper WB calibration and to guard against drift by directly monitoring exhaust temperature. The private tuner, not so much.

As far as Banish goes, I'll read very carefully anything he has written - that's free training.

I think murphinator said it best on Mar 29;
"start with Greg Banish's book engine management and tuning $20ish depending where you buy it and the help files and stickys at the top of the forums

you can get accurate data to tune with from your stock narrowband 02 sensors as long as you dont ask them to do what they cannot

narrowband is only accurate from approx 14 to 1 afr to 15 to 1 afr so you can tune idle and part throttle with some level of confidence that you are close

the problem is you want to tune WOT thats why you bought hpt and all your bolt ons. 3800 sc needs to be mid to high 11's afr or you will chip pistons on the middle cylinders (3 in particular) so you need a wideband to tune wot since it is accurate over a wideband of 02 readings including that 11-12 to 1 afr area you will want to be working in with a 3800sc

fyi all widebands are not created equal either so do your research before $$ for a wideband only to again find out you dont have everything you need to tune properly. the afx with ntk sensor is the unit most on here feel has the best accuracy for units under $1000 and its about $360"

[Perforator]

As eficalibrator (Greg) stated in a different thread not too long ago that GM uses widebands on every engine dyno to build those fueling maps in the first place.

This is true but as soon as you modify your engine all those fueling maps are inaccurate and since the PCM uses the narrowband for fueling closed loop why shouldn't you use it to tune closed loop?