recurring front O2 sensor code

[t5ftw]

Stock exhaust?

Except K&N filter, H&R spring, and Bilstein strut, everything else is stock including new spark plugs.

[t5ftw]

Are you the one that lives around Blacksburg? I'm sure the code will return - if you want to stop by some time next weekend (I will be out of town this weekend), I can try to figure out what's causing it to come back. My guess, though, would be that something's letting unmetered air into the system and annoying it.

Yeah, I am in Blacksburg. If you can take a look at, that would be really great. I also wanted to have some other T5 owner try my car and see how close mine is to its normal state.

[t5ftw]

Unmetered air is a strong possibility and Anything related to the A/F metering is possible, but I also noticed you said that the rear O2 was also replaced not to long ago. If they are not of the same type/manufacturer this code can also set. The ECM compares the front and rear O2 adaption values and if the signal varries by more then 3% this DTC will set, and both the front and rear can set the same code. Also it should be noted that with the dealer tool P1132 translates into ECM-280A, which has four diffirent types of fault:

Signal too high
Signal too low
Signal Missing or,
Faulty signal

As you can see this leaves multiple avenues for diagnosis

First thing to do in the evening. I will make sure if my rear sensor is the correct one and the connection is secure. I can see how it will be useful to have live data scanner. I am thinking about vol-fcr, but need some research on whether this actually worked for people or not.

[t5ftw]

I checked the rear O2 sensor, and it was OEM with Volvo part number on it. I am rather not sure if my front sensor is the correct one. I ordered scantool.net pc-based tool, I will come back when I get some test data. I also used a bottle of techron. It did not stop the code coming back, but it seemed to delay it. It came back after 200 miles with additional code P0141. I think I might have vacuum leak too, but not significant enough for me to notice. How much unmetered air are we talking about here to cause problem like this? I am considering replacing vacuum lines with the ones from stylinmotors. but their kit as I heard comes with zip ties instead of clamps. Will this zip tie be sufficient for the application?

[t5ftw]

Finally, I got a scantool.net cable and SW (OBDwiz) and run a short test. Before I throw my data, I want to explain what has been going on. When I get O2 code, I feel the car getting sluggish (but still its an awesome ride. not really bad at all.) Then, I disconnect the battery, and try starting the engine a few times to discharge and clear ECU. When I reconnect the battery, the car feels restored. Then, it gets progressively worse little by little and I get the code again in 3-7 days. I have been repeating this for a while. So, what people has been saying here are bad MAF, bad O2 sensor connection, incompatible O2 sensor, leak around O2 sensor, vacuum leak and unmetered air, bad fuel injector and may be there was more.
I still have no clue what is causing my problem, but I got some data so that you can take a look and make more informed guesses.
Currently, I have no code or CEL on. I have been driving about 70 miles since I reset ECU a couple of days ago. However, I feel the car is getting sluggish especially when it is hot outside 90*F. I wouldn't be surprised if I get CEL on now.

[t5ftw]

Now, I have two more sets of data. One set records when CEL comes on, and the other records after the reset. In the following two plot you will see when the front O2 sensor stopped working and the LTFT keeps increasing until it reaches a certain point since the reset.

[t5ftw]

Ok, I did my homework and calculated Air-Fuel-Ratio. Still, I am not sure what I am doing is correct. Based on the data collected from two test runs, when CEL came on and after ECU reset,

When CEL came on
Mean (throughout the run)
Air: 2.3 lb/min = 2.3 lb/min x 60 min/hr = 138 lb/hr
Fuel: 1.6 gal/hr = 1.6 gal/hr x 6.15 pounds/gal = 9.84 pounds/hr

AFR: 138/9.84 = 14.024


at Max load (around 16 min)
Air: 15.8 lb/min = 15.8 lbs/min x 60 min/hr = 948 lbs/hr
Fuel: 10.5 gal/hr = 10.5 gal/hr x 6.15 pounds/gal = 64.575 pounds/hr

AFR: 948/64.585 = 14.681


After ECU reset
Mean
Air: 2.3 lb/min = 2.3 lb/min x 60 min/hr = 138 lb/hr
Fuel: 1.5 gal/hr = 1.5 gal/hr x 6.15 pounds/gal = 9.225 pounds/hr

AFR: 138/9.225 = 14.959


at max load (around 6 min)
Air: 13 lb/min = 13 lbs/min x 60 min/hr = 780 lbs/hr
Fuel: 8.6 gal/hr = 8.6 gal/hr x 6.15 pounds/gal = 52.89 pounds/hr

AFR: 948/64.585 = 14.748

So, according to these results, ECU is doing the right thing as long as the MAF and fuel sensor are generating the correct data, right? In this case, most likely the front O2 sensor is also doing nothing wrong considering its voltage range (0-0.7V) and the mean value (0.5V), which is consistent thought all three test runs. The only thing weird is that the ECU stopped reporting STFT when CEL came on even though the front O2 sensor voltage seems normal.
My guess on the increasing LTFT right after ECU reset is that the ECU is adapting to the high-flow K&N filter. So, it is how it supposed to be, settling around 11.7. But when CEL came on, LTFT was around 14.8, which is about 3% higher.

Any insight?

Other questions I have are how to calculate expected air mass entering? So, at Wide-Open-Throttle, MAF should report how much air mass? If I don't have WOT data, can I use the calculated load value and compute the proportional value of air mass at WOT?

EDIT: I just discovered that this tool I am using calculated fuel flow by a formula like this Fuel Flow Rate = MAF x Target Air/Fuel Ratio. So, this is putting me back to where I started.

[nightc1]

I'm going to tell you my story and take from it what you will.

On my 99 V70 my car threw the front 02 sensor code and codes related to a real problem I have with my ABS. After much searching it ended up being my fuel relay which throws no codes but can do a number on the fuel system and throw 02 codes.

After putting a jumper in place of my relay and driving my car around (which mine finally died and meant my car didn't start and run for very long) and then driving the car around with a jumper in place of the relay I noticed the O2 sensor code hasn't come back.

Again, this isnt' the magic fix for every problem, but definitely try running the car without the relay and see if the problem persists. If it does, I'd look at the gas cap (check for pressure release when taking it off, if it's not there, that's not normal)... and replace the fuel filter if it has been a while (as that to can choak a system). Also the Idle Air Control Valve can easily be removed and cleaned. On my 99V70 it was located on the main air line (actually screwed to it under a black cover) between the MAF and ETM... with a hose running out the other end up and then under the fuel rail.

This is just my 2 cents. It may not help at all but in the off chance it does, I figure it couldn't hurt to check a few other things.

[t5ftw]

So, you are talking about the fuel pump relay in the fuse box? I will definitely take a look at it and see if I can find some jumper in place of that. As far as I remember, it looked like a cube with four pins. Did you need custom wiring for jumping?
I replaced fuel filter less than two months ago, and the one that I took out had been on 15,000 miles I did not know until I took it off and saw the miles written on it. I was not having a problem but I just did it because I decided to replace all the filters. I also replaced the gas cap three months ago as soon as I purchased this car. However, I do not notice pressure release when taking it off.
I don't remember seeing anything like idle air control valve. I will search for it based on your description.

EDIT: Ok, I found fuel relay. I replaced MAF sensor but made almost no difference except that it feels tiny bit smoother. In fact my car runs rich. I let someone drive my car and followed it. At hard acceleration, I see black smoke coming out of tail for a second. But it is not too much. So I could not see it in mirror when I drive. Which sensor affects fuel trims? Is it only the pre-cat O2 sensor or both pre-cat and post-cat? Is LTFT is average of STFT over certain period? I am looking at data of PID "oxygen sensor voltage, short term fuel trim (bank 1 sensor 2)". What does it mean exactly? Does it mean that the post-cat sensor reading is used to adjust short term fuel trim?
I got another code P0137, and the scan tool I have showed the following info saying that the sensor has failed one test. Can this be the source of my problem or just a result of my problem?