O2 readings

[Sonataman]

My car has an NTK 5 wire O2 sensor so I assume it's a wideband O2. If that is the case why does my Ultragauge give readings from .1-.9 volts instead of 0-5 volts?

Been trying to chase down a reason for falling MPG, it's dropped 8-10 mpg in the past 8 months.
Thought at first it was bad gas, but after trying different grades and stations, it continues to go down.

Cat temps are normal as is oil temp so I don't think the calipers are causing brake drag.

Short and long fuel trims HAVE changed with the long reading richer, the commanded AFR which reads in Lambda also reads richer.

No CEL either.

Help.

 

[slowdime]

Does the ultragauge allow readings higher than .9 volts? If it's the car in your sig it the o2 sensor shouldn't be going out this early. Is it still under warranty?

 

[toyota62]

Two steps 4 wire O2 sensors switching voltage 100mV to 900mV.
100mV High oxygen content-Lean mixture. 900mV low oxygen content Rich mixture.
The Transition from rich to lean occurs quickly at about 450-500mV.(A/F ratio 14.7:1 or lambda =1)

 

[SHOZ]

It's probably the Ultragauge limit as far as not reading above 1V.

You can connect a voltmeter to the 5th wire and read the voltage then calculate the AF ration.

V/.3324+7.35=A/F ratio

 

[eljefino]

Wonder if your injectors aren't balanced or you have an IM gasket vacuum leak.

 

[Oldmoparguy1]

You have a vacuum leak somewhere. The ECU is reading too much O2 so is adding fuel. A cylinder misfire will cause the same thing but you can usually feel that. The O2 sensor reads O2, not fuel. It can be pig rich and still read too much O2.

 

[Vikas]

By the way, many OBD-II AFR O2 readings are converted in to old style O2 readings before displaying.

 

[ARCOgraphite]

Got to scope the sensor voltage and look at the cycle freq to ascertain a slow sense.
You may have a poor spray pattern on one injector or air leak in the IM trac or EX as has been suggested. I'm down 4mpg with a black ex pipe also on the Rogue. Went bad after 1 bad tank of fuel and never recovered. 20 mpg on a 4cyl, 3400 lb car is not acceptable.

 

[Vikas]

Quote:
Got to scope the sensor voltage and look at the cycle freq to ascertain a slow sense.
Wide-band (AFR) sensor does not cycle. It remains at steady value.

 

[SHOZ]

Torque Pro and the Hyundai Advanced plug in for it will read the WBO2 reading and the ECU commanded AFR. You an compare them as well as the O2 voltages.

 

[Sonataman]

All plugs look the same, darker than the original set I replaced last year, especially on the base ring.

Commanded AFR Lambda readings under normal driving are always .989 to .997
Used to run .995 to .997 at all times when warm, now stays in the .989 to .993 range more often.

O2 readings start at .450 on a cold start and then go to .65 to .800 when warm.

Long term fuel trim used to run -5 to -10% and now runs -3 to +2%

Where should I look for an air leak?

Anything done until I get a CEL will be out of pocket so hope its an easy fix.....

 

[Vikas]

Quote:
Long term fuel trim used to run -5 to -10% and now runs -3 to +2%
That means everything is now perfect.

 

[Sonataman]

Picked up a new Ultra Gauge and it shows both O2 sensors, the wide band (before cat) and narrow band (after cat). It reads Lambda on the wide and volts on the narrow (like the old one).

More info-
Wideband O2 reads on average what the commanded AFR shows, .990-.997
Narrowband O2 reads .6-.8 volts most of the time.

Fuel trims still reading same.
Map reads .1 PSI under what my Kestrel shows.
Baro reads .6" Hg under what the Kestrel shows. (?)

EGR Purge comes on before the engine is even warmed up, but cycles on and off. More throttle nets a higher % purge until cresting 3 gph then it switches off. Off throttle when in EGR cycle reads 2.75% and at idle it shows 21%. According to my understanding of how and when it is suppose to work, mine is not working correctly.

Sometimes on a longer trip (50 miles) it will cycle on and off 5-6 times and at other times it will only cycle on once.