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Discussion Starter · #1 ·
2006 outback 2.5i with 135000 miles


For the past few months I have been having the po171 code intermittently occurring. It all started after I had a misfire code and quickly changed the plugs and wires and that fixed the misfire. The next day the po171 code came on, and there has been almost no noticeable problems except for maybe a little bit of a rough Idle sometimes. Also the car has always had a sort of a hesitation when you hit the gas pedal, but somewhat went away after plugs and wires were changed. To attempt to fix the po171 code, I have already cleaned the maf sensor, changed the pcv valve, used injector cleaner, and attempted to check for vacuum leaks. Nothing has got the code to not come back, i cleared the code about a month ago and it hasn't came back until yesterday when I was driving for 2 hours on the highway. I'll put up the freeze frame data. The only things I can think of left are the fuel filter maybe?, stuck Injectors, or vacuum leaks I can't find? Does anybody have any recommendations? Thanks!




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2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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front passenger side a/f (o2 ) sensor = sensor1 bank 1,

that controls the whole car with its data, and causes such codes / misfires., and does get old and dirty.

get a Denso from Rockauto / amazon etc. $70-$110 depending upon the car.
 

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and with that many miles / years, in areas with salt/calcium etc. on the roads

o2 sensors may not come out easy. but still quick work for a shop with a lift if need be. (like half a hour).
 

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2008 Outback 2.5i
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Lean at ~3000 rpm... maybe check the pcv breathers that go from the valve covers to the air box on both sides, maybe one got loose with the work you did.
 

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According to the mfr website, the Foxwell NT301 can display OBD data in real time. While the freeze frame data tells us what the conditions were at the precise time the CEL was turned on, there might be more leads to causes when looking at the data at different rpm and load conditions. For example, it might be helpful to see what's happening with the fuel correction (both ST and LT) and the A/F Sensor (B1S1) and O2 sensor (B1S2) at idle. If there is an intake air leak it should show up at idle as well.

The fact that the CEL didn't come on for about a month after being cleared doesn't mean the fault wasn't there; rather it might only mean that the criteria for triggering the CEL wasn't met. For that code, unusually high fuel trim has to be detected in two consecutive drive cycles, where the fuel correction triggering criterion (i.e., total percentage) varies with engine rpm and load. So it take a combination of factors to lead to the light coming on. By using the Foxwell's capabilities, it should be possible to see if there are unusual conditions at times other than when the CEL is actually turned on.
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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LTFT seems to indicate a small vacuum leak?

easy enough also to try cleaning the MAF
 

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LTFT seems to indicate a small vacuum leak?

easy enough also to try cleaning the MAF

more coffee.

" I have already cleaned the maf sensor, changed the pcv valve, used injector cleaner, and attempted to check for vacuum leaks."​
 

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^^ good idea!

ha!
 

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what brand plugs and wires? Many folks report our cars not liking aftermarket parts in these locations.

or maybe a plug's electrode got banged-up on installation?
 

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Discussion Starter · #10 ·
what brand plugs and wires? Many folks report our cars not liking aftermarket parts in these locations.

or maybe a plug's electrode got banged-up on installation?


I Belive they are ngk plugs, and oem wires from the dealership, I might end up taking them back out to check them again!
Thanks


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Discussion Starter · #11 ·
According to the mfr website, the Foxwell NT301 can display OBD data in real time. While the freeze frame data tells us what the conditions were at the precise time the CEL was turned on, there might be more leads to causes when looking at the data at different rpm and load conditions. For example, it might be helpful to see what's happening with the fuel correction (both ST and LT) and the A/F Sensor (B1S1) and O2 sensor (B1S2) at idle. If there is an intake air leak it should show up at idle as well.

The fact that the CEL didn't come on for about a month after being cleared doesn't mean the fault wasn't there; rather it might only mean that the criteria for triggering the CEL wasn't met. For that code, unusually high fuel trim has to be detected in two consecutive drive cycles, where the fuel correction triggering criterion (i.e., total percentage) varies with engine rpm and load. So it take a combination of factors to lead to the light coming on. By using the Foxwell's capabilities, it should be possible to see if there are unusual conditions at times other than when the CEL is actually turned on.


Alright thanks a lot! Will have to try out the live data feature!


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Discussion Starter · #12 ·
Update:

Light still comes on for the same po171 code. It always comes on at about 65 mph on the highway. Since the last update, I changed both oxygen sensors, so I am really at a loss. Could it be the fuel filter? Maybe I need to get a professional to do a vacuum test?


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kinda wondering if, while observing live data at idle, you could wiggle vacuum lines around and find a leaker. Or spray some brake cleaner or starter fluid around the intake manifold and see some change in fuel trim or ???????
 

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Discussion Starter · #14 ·
kinda wondering if, while observing live data at idle, you could wiggle vacuum lines around and find a leaker. Or spray some brake cleaner or starter fluid around the intake manifold and see some change in fuel trim or ???????


I'll try doing that with live data on. I've already attempted straying some starter fluid looking for a change in idle but was unsuccessfull. I'll try doing it again and look at fuel trim. Also I even tried to cigar test with no luck!!!!


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