So quite awhile ago i installed an AEM UEGO Wideband. So at first i just plugged the sensor into the open bung to get rid of the raspy sound in my exhaust. It wasnt hooked up to anything since i hadnt had a chance to run the wiring harness down to it yet. Well i drove it like that for a few weeks then got some time to run the harness to it. Plugged it in and the A/F's jumped around a little. They hang around 14.8 for the most part at idle but they will randomly jump from 13 to 17 and everywhere in between. So, i figured maybe i had a bad sensor since i had it installed with no power to it. So i replaced it with a "new" on from somebody on here. It appearred to be new, grime on it or any signs of use. Plugged it in and its still does the same thing. Now my 2nd O2 sensor is about 4-6" in front of the wideband sensor. So i figured maybe that was causing an issue. So removed and plugged the 2nd O2 sensor hole. Still does the same thing. The wideband responds like it should for the most part (rev and it goes rich, then lean, then hangs around 14.8 again...but still jumpy). My tuner says everything is fine on the many logs ive sent him...

So why the jumpy A/F???

Here is a video of idle when the engine is warmed up..then a little rev.

2009 cobalt ss wideband - YouTube

 

mine does the same thing. and i am also havin an issue with boost and im at this point thinking its the gauge

btw i have the same gauge.

 

hmm. yea i cant figure out why. i have done boost leak checks too and coming up with nothing. Im not having any issues with boost tho. I think im going to sell it/get rid of it and just get an interceptor

 

im havin issues with there boost gauge im not even seeing any vacuum lol

 

I think that is normal, mine does the same shot at idle it moves back and forth between 14 and 15 and if i give it gas it goes rich then when i let off it goes lean into the 17+, now when i go wide open trottle it dont bounch like that it just starts to rich up and caps out around 10.8 to 10.9 until i back off, james (ccss3) explained it to me like this when its idle and just driving reg its in open loop and when i got wot it goes closed loop, it believe that means ot reads differently during closed loop vs open loop

 

is that just an LNF thing? Cobalt thing? Ecotec thing? Cuz my buddies SRT4 doesn't do that. it doesn't fluctuate more than a few tenths. Almost seems pointless to have the gauge if it is "normal" to be bouncing around like that.

 

"Mixture

The air/fuel mixture is expressed either as the ratio of air to fuel vapor or as a lambda value. The lambda value is derived from the stoichiometric air/fuel ratio, which is the chemically correct ratio of air to fuel for complete combustion to take place. The stoichiometric ratio is 14.7:1 when expressed as an air/fuel ratio, or 1 when expressed as a lambda value. A richer mixture will have a lower air/fuel ratio and lower lambda value. e.g. an air/fuel ratio of 12.5:1 equals a lambda value of 0.85, and is a typical value for a naturally aspirated engine under full load.

Stoichiometry

The ECU aims to keep the air/fuel ratio close to the stoichiometric air/fuel ratio in order for the catalytic converter to work at maximum efficiency. This air/fuel ratio also gives good fuel economy. Under increased engine load the optimum air/fuel ratio is richer than the stoichiometric air/fuel ratio in order to give maximum engine output and prevent engine damage.

Oxygen Sensors

An oxygen sensor produces an electric voltage from the different levels of oxygen present in the air and the exhaust gas. If the mixture is rich then the exhaust gas will contain very little oxygen. The oxygen sensor will therefore product a voltage output, which the ECU senses and determines that the fuel mixture is rich. Conversely if the fuel mixture is lean then the exhaust gas will contain higher levels of oxygen, which produces a lower voltage output. The normal range of the oxygen sensor output signal is about 0.2V to 1.2V It should be noted that most stock oxygen sensors are designed to be particularly sensitive around the stoichiometric air/fuel ratio.

Closed Loop

In closed loop operation the ECU uses one or more oxygen sensors as a feedback loop in order to adjust the fuel mixture. This gives the name ‘closed loop’ from the closed feedback loop. The ECU won’t run in a closed feedback loop all the time, so ‘open loop’ is used to describe the operation of the ECU when the mixture is not being adjusted in this way (usually when the engine is cold or when running under high load).

In closed loop operation the ECU uses the oxygen sensor to tell if the fuel mixture is rich or lean. However, due to the characteristics of the oxygen sensor it can’t tell exactly how rich or lean, it only knows that the mixture is richer or leaner than optimum. The ECU will enrich the mixture if the oxygen sensor shows that the mixture is lean, and lean the mixture if it looks rich. The result of this is that the mixture will swing back and forward around the stoichiometric point."




Here is some good info that pertains to this. I bolded a part that explains closed loop and it mentions the bouncing back and forth from "ideal ratio" or stoich.

 

Well i have an lsj and mine does pretty much same thing after it warms up a lil bit, ill try and get a videl of it and post it. So im pretty sure its how it just works but i honestly could be wrong lol. Also the point of the gauge i to make sure u dont go too lean during wot, i know mine works just fine during wot have u tested urs yet?

 

yes i have tested it. but i cant remember what it goes to during wot. Could a fouled first O2 sensor cause it to bouce around? (more than normal maybe).

 

Here may be the reason, when I was modding my talon, I did alot of research on af gauges, everyone said that the sensor must be within 8 inches of the o2 housing , after that it becomes more and more inaccurate the further away u put it, and the second 02 bung is quite far away. Could be the reason

 

That would explain why my logs are showing good ratios in HPT. becuz it reads off the first O2 sensor which is at the end of my O2 housing. (my O2 housing and downpour are one piece tho)

 

It's doing that because it wants you to run E85.

 

Shoot I want to run e85 but Tuner James says no es no possiblč

 

Why did you buy a wideband? Lnfs have a wideband stock.

 

+1. You need to graph commanded vs actual. Just having an independent wideband is serving you no good, because you can't see what the ECU wants.

It is SUPPOSED to swing lean when you come off the throttle, which is what it did. An aftermarket wideband on this car is money in the toilet.

 

I guess I wanted a gauge dedicated to monitoring air/fuel.

 

Buy an aeroforce scan gauge. Its well worth the money and you will love it trust me.

 

Monitoring LTFT and STFT are more useful via Interceptor, or HP Tuner.

 

^^^ THIS

Did you tell your tuner that you did this? He should be familiar enough with the LNF to tell you you shouldnt have needed one.

x2 on the Interceptors btw. You kinda threw money out the window on a second wideband.

 

Mine jumps to 29.3 when I let off the gas under 3k.

 

It's normal Bryce. Your car can do a little e but not much. Within all the logs, the Afr does commanded. Send another log to me if youd like. Which I'd like one anyways. David I already told you its normal deacceleration dual cut off.

 

Yea I figured it was somewhat normal tuning wise, I was just curious if something was wrong install-wise with my gauge or sensor.


So....anybody want a wideband?? Lol