So long story short I am chasing what I believe to be a rich condition for my 04 V70. Now I do have access to a fairly reasonable scan tool of which is able to Graph, Record and Stream live data. However I am unfamiliar and unsure of the current fuel trims or whether or not the O2 sensors are working adequately. I haven't in my research been able to find O2 sensor readings or fuel trim readings to compare to and frankly I'm also not sure if the O2 Sensors in these cars are any different than others in any respect. That said my readings are as follows:
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My front O2 sensor "flatlines", it stays around 1.00, rarely dipping around 0.89, usually stays at 1.00 and 0.98 respectively. However this sensor does not respond or if it does it does very slowly when giving throttle input or staying at 2,500rpm.
My rear O2 sensor reads anywhere between 0.72 and 0.20. I suspect the rear is doing fine as it oscillates up and down as a functioning correct sensor does (albeit lazily, which could be a symptom of the front perhaps not functioning correctly?).
My long term fuel trim sits at .97, while my short term fuel trim sits at 1.02, but this fluctuates. AFAIK, a good fuel trim reading is usually in most cases +/- 3-6%, or thereabouts.
My fuel pressure is 55 PSI for what it's worth, though I am unsure of regular fuel pressure at idle is for these cars.

I did recently change the spark plugs, oil and oil filter and a couple of the spark plugs did have gas on them, suggesting a rich condition. No gas in the oil as far as I can remember. No engine codes, and the car runs perfectly fine outside of what I believe to be a rich condition, (smell, spark plugs, etc.). I did take off the throttle body and cleaned it, the plate was fairly carboned up. (though I am unsure of if doing this helped any as I forgot to take any readings prior to the cleaning, only after). I did look at my fuel injectors and they look kind of grimey -- though the front O2 sensor not doing much has given me the most in terms of eyebrow raising.

Any insight would be appreciative. Thanks!

 

Are you getting fuel trim codes? That come back after clearing? Or do you just "think" your car is running rich?

 

No, I'm not getting any codes. The car is actually running/driving fine. That said, I did find gas on my spark plugs and O2 sensor/Short term/Long term fuel data suggests that it may be running rich. As I said in my post, the front O2 sensor barely does anything. It's stuck sitting around 1.00, sometimes goes to .89, but mostly sits around 1.00 and .98. The sensor also doesn't oscillate as a normal sensor usually does (the rear sensor does, albeit lazily), it doesn't respond to throttle input either. Now I could just be losing my mind and truthfully I know very little on Volvo emission systems, so perhaps this car smells a little more "gassy" than I am used to, but I want to make sure all of my trims, O2 sensors and what not are correct. The car does have 138k miles, and I've seen people say these sensors go bad around the 100k mark, but I bought the car after the 100k mark, so I'm not sure of its past history.

I forgot to put that my car is the non-turbo Volvo V70, with the 2.4.

 

If your fuel pressure/fuel trim/O2 signals/air mass signal/etc were out of spec - a code or more would be set. And if a signal is bad enough for long enough - the check engine light will come on.

You found "gas" on your spark plugs. How do you know it was "gas"?

 

I expected a code as well, but alas after driving the car for approximately 500 miles, there hasn't been a code set. I suspected a rich condition prior to driving said 500 miles fully expecting a code, but the car behaves normally despite what the live data suggests. I'm not sure if the front O2 sensor is working JUST enough so that it isn't throwing a code but the lack of oscillation and 1.00 "flatline" more often than not raises eyebrows for me. I could be overthinking it, or rather underthinking, but that's why I wanted some proper insight.

As for finding gas on my spark plugs, I smelt the plug and regrettably tasted it and it is definitely gas. Mind you, the previous owner put Autolite plugs into the car, so perhaps the car had a distaste for them, I swapped them for OEM Volvo straight from FCP Euro. Like I said, I am unfamiliar with Volvo emission systems. My fuel economy for the highway is anywhere between 26mpg to 30mpg, in the city it sits around 16mpg to 18mpg, since I swapped the plugs I did achieve 20mpg city. Not sure if this is normal or bad economy, but I figured I'd mention it nevertheless.

 

Earlier "Narrow" band O2 sensors are simple - .2 volt = very lean, 1.2 volt = very rich. And I certainly expect to see oscillations from ~.2-.7 volts on a simple volt ohmmeter or scan tool during normal operation, once the sensor is in closed loop (a minute or so after starting, after the ECU thinks the sensor is hot enough for a correct reading) - If your car has a wideband front sensor (it does) that earlier way to measure voltage output and equate that to correct operation is not valid.

The catalytic converter converts CO and HC into CO2 and H2O using the O2 left after combustion. In theory at the rear O2 sensor there should be very little O2 left, and with a narrow band sensor - a very low (.2) and relatively stable voltage. I don't know if the rear is wide or narrow band. Most were replaced at my shop due to bad heaters and we never checked the output voltage while diagnosing power to the heater. It seemed measuring O2 sensor voltages was no longer needed once wideband sensors were phased in and I starting using used the diagnostic capabilities of VIDA to help with repairs on 99+ cars.

What I am saying is that your measurement of 1 v on the front sensor - is probably normal.

I found this quote - in a automotive trade magazine. https://www.brakeandfrontend.com/wid...e-differences/

"A quality scan tool can be used to test a wideband sensor, but be aware that many aftermarket scan tools display AFR sensor data in conventional sensor voltages or some other data stream such as lambda or milliamperes, which can be confusing even for an experienced tech. Depending on the model, some AFR sensors use pulse modulation, in which case, an amp probe or scope is better for testing amperage or current flow. The mechanical and electrical construction of today’s AFR sensors has become more complex and application-specific. Be sure to look at what the manufacturer uses for data output on a specific model before testing, or you’ll be scratching your head for a while."

 

Thanks for the reply. I appreciate your help in understanding this car a bit more, so any insight is very useful and helpful to me. I'm fairly used to seeing oscillation in the live data when diagnosing o2 sensors, so when a sensor is flatlining or not even showing adequate adjustment when blipping the throttle or holding it above 1,500 rpm it raised suspicion for me. It makes sense in that it is wideband, I was unaware that the front one was wideband and you are correct when citing the article as my scanner reads the front as "lambda", however the rear is read normally and offers the oscillation I expected when reading the data.

That all said, I am unsure of how to read my Short/Long term fuel trim. They seem overly rich, and I did read all the data while the car was warmed up at operating temperature. That and there was gas on the spark plugs, but it may very well be that the car didn't like the Autolites that were in it. The car doesn't have any real drivability concerns or issues outside of the aforementioned, and the rather gassy smell it possesses at idle. If my short/long term fuel trims are reading rich, and I can rule out the O2's, then I suspect maybe the injectors and maybe the PCV? Not sure when the PCV was done, if at all on this car, and I've read that the PCV's on these cars are somewhat notorious. The rather carboned up Throttle body may of been a good sign that the PCV needs done, however I did the old glove trick and stuck it over the oil filler and it did not display any issues with a potentially clogged or clogging PCV, but it may very well be on its way out and thus causing a rich condition as a first sign. (Provided I am even reading my short/long term fuel trim correctly), but the numbers I posted are the ones given, so any insight on that would be great. Thanks again!

 

I have 2009 s80 having the same issue. Front O2 reading is about steady 0.9 v. Rear O2 is swinging between 0.2-0.9v. I have check engine light.
it is not normal for sure. The front one should fluctuate between 0.2-0.9v and rear sensor should be around 0.45v.
I have trouble to remove the front O2 sensor.
my long short terms are both around 0%. I believe the resistance of O2 sensor is open when heat up. So ecu decline to use the data from O2 sensor

 

Yes, if you had the old style narrow band sensor. But you do not. Read the above article for more information, then reevaluate your diagnosis.

 

I would read what Hoonk has provided. I was unaware that the upstream sensor was wideband, thus normal diagnosis of o2 sensors doesn't necessarily apply the same way. That being said, you said you have a check engine light....what is the code?
I did do a bit more research on Wideband diagnosis and readings, largely from people like DiagnoseDan on YouTube and he has said you can better read wideband on generic OBD2 data. I have yet to try it, but it may be worth looking into.

 

It is old style O2 sensor, not wide band for 2009 s80. I use vida to read the data and code. P0031, O2 sensor circuit low.

 

Everyone's entitled to their opinion. I developed mine from this information in VIDA stating front and rear O2 sensors are not the same type and that the front can't be "read" using a multimeter.

 

Even the wideband O2 sensor, the front should swing and rear should stable. The front send the signal feedback to ecm to adjust air/fuel ratio. The rear one monitor the final exhaust gasses to tell if catalytic converter is working or not.

 

Side note - Wideband (WB/AFR) sensors do not swing like a narrow band. WB at with AFR at stoich will be around 3v. You will see it move slowly (ramp up or down) if you bump throttle to 3K rpm to vary engine fuel needs.

Testing rear O2 sensor requires cat at operating temp and engine held at 2500rpm. You may see some slight cycling from .2 to .9v. It should not be active like you would see on a vehicle with a front O2 NB sensor. If so, cat is not working as expected. If sensor output is sitting around .45 - .5v (high/low threshold), verify sensor is working by inducing carb spray or vacuum leak. If sluggish or not cycling to sensor limits, replace sensor.

 

Thank you guys. You are correct. I thought my S80 was narrow band O2 sensor. It actually a wide band sensor. vida reads 0.8-0.9 v, not 3.x v.