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Old 09-07-2019, 02:23 AM   #1
epeder1102
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Default Cruising and Idling Extremely Lean?

I just installed an AEM wideband into my 2004 WRX. The car is fairly new to me, my second WRX. The problem I am seeing is that for normal around town driving the AFRs seem normal around 14.7 to 15.3 at idle and low speed cruising and becoming fairly rich under boost. However, the other day I got on the highway and cruised at 70 and slowly watched the AFR creep higher and higher. After about 45 mins of cruising my gauge was maxed out, meaning AFR > 18.0.
This scared me so I pulled off the highway, noticed idle was maxed AFRs too and reflashed my tune via the accessport. Upon restart idle seemed normal, but when getting back into cruising at 70ish, the AFRs maxed out much quicker than before. Everything else about the car seems normal. It pulls hard and becomes nice and rich under boost. No hesitation or stuttering. Idle is perfectly normal even when the AFR was maxed. I'll attach a picture of my accessport numbers from when I pulled over, just before I reflashed the tune. I do get some knock numbers once in a while but DAM never drops below 16. AF Learning is never negative, which I think means it is always adding fuel...could maybe point to a possible problem? I'm not sure where to start here since the car seems normal otherwise and although I know the stock front O2 sensor isn't very accurate, it still never read more than 15.0 at idle or cruise the whole time when looking at the accessport AFR. Maybe I have a faulty wideband sensor for my AEM gauge? Any help would be appreciated, I'll list my mods below. Thanks.

EDIT: Forgot to add that there are no obvious vacuum leaks, however I have not done a proper boost/vacuum leak test yet. Seems to me that if that was the problem it would run lean right away not just after some time of driving. The problem consistently happens after 20 to 30 mins of driving on the highway. Also, there is no check engine light on.

2004 WRX
P&L Motorsports Catted Turboback
Cobb SF Intake
P&L Motorsports Catless Uppipe
Cobb OTS Stage 2 91oct Tune via Accessport V3

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Last edited by epeder1102; 09-07-2019 at 02:30 AM.
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Old 09-07-2019, 12:12 PM   #2
wrxlaunch
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When at idle... wait 30 seconds, what is your A/F and what is your A/F learning 1 ?
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Old 09-07-2019, 01:10 PM   #3
subaru_gc8
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if it were that lean it would buck like a horse..if it running fine, then you would be okay
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Old 09-08-2019, 03:29 AM   #4
epeder1102
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Quote:
Originally Posted by wrxlaunch View Post
When at idle... wait 30 seconds, what is your A/F and what is your A/F learning 1 ?
When I haven't been driving for long idle stays at 14.7 to 15.0 with a 4.69ish AF learning 1. AF learning 1 varies from 2 to 8ish day to day it seems. However under high boost AF learning 1 drops to zero every time.
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Old 09-10-2019, 01:01 PM   #5
jzapatajr
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Maybe the issue is with the sensor? Bad sensor?
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Old 09-10-2019, 01:12 PM   #6
86Dreams
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so the aem wideband is which model? where is the sensor installed?
Which gauge is it that
Quote:
After about 45 mins of cruising my gauge was maxed out, meaning AFR > 18.0.
? Is it the one in the picture? and if so is it the big number or little number?
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Old 09-14-2019, 09:16 PM   #7
epeder1102
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So today I drove a tank of gas purely on the highway and I calculated the gas milage for that tank to be 29mpg!! Not sure if I am correct, but that seems way too high compared to my old stock bugeye that got a max of 24mpg. This supports the gauge that the car is running extremely lean, as it was maxed out the entire trip...but the car is still running flawlessly...

Quote:
Originally Posted by jzapatajr View Post
Maybe the issue is with the sensor? *Bad sensor?
I am in contact with AEM, so far all they said was it could be a bad sensor or a bad gauge and asked for a bunch of my info...not very helpful yet.

Quote:
Originally Posted by 86Dreams View Post
so the aem wideband is which model? where is the sensor installed?
Which gauge is it that ? Is it the one in the picture? and if so is it the big number or little number?
Its a AEM UEGO 30-4110 with the sensor installed on the top side of my downpipe about 8 inches from the turbo. The gauge that gets maxed out is the AEM gauge, I just included a picture of my accessport to show that nothing else seems out of whack when the AEM gauge is reading super lean. The AFR reading on the accessport from the stock upstream O2 sensor is always good, but I know that sensor is not always very accurate since it is a narrow band sensor.

I could also take some cruising logs with my AP, just not sure if that would be helpful or not.
Wouldn't the car throw a CEL if I was really running that lean? I do have a CEL now but it is a P0442 for a small evap leak which seems unrelated.

Last edited by epeder1102; 09-14-2019 at 09:33 PM.
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Old Yesterday, 06:18 AM   #8
subaru_gc8
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did you calibrate it correctly?

the stock sensor is fine. if they stock sensor is crap you car wouldn't run dont write if off , that is where your car is taking all of its readings from. I mean think about it when you get tuned, the tuners dont use the wide bands, they use the readings off the oem o2
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Old Yesterday, 11:27 AM   #9
epeder1102
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Quote:
Originally Posted by subaru_gc8 View Post
did you calibrate it correctly?

the stock sensor is fine. if they stock sensor is crap you car wouldn't run dont write if off , that is where your car is taking all of its readings from. I mean think about it when you get tuned, the tuners dont use the wide bands, they use the readings off the oem o2

The AEM UEGO supposedly never needs calibration. Also, I could be wrong but I am pretty sure a lot of tuners won't even touch your car without a wideband. I will be running some injector cleaner through the system and cleaning the MAF sensor in the next few days to see if that makes any difference. Hopefully AEM will get back to me with their opinion soon.
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Old Yesterday, 06:07 PM   #10
subaru_gc8
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Quote:
Originally Posted by epeder1102 View Post
The AEM UEGO supposedly never needs calibration. Also, I could be wrong but I am pretty sure a lot of tuners won't even touch your car without a wideband. I will be running some injector cleaner through the system and cleaning the MAF sensor in the next few days to see if that makes any difference. Hopefully AEM will get back to me with their opinion soon.
yeah I dont know about that, I know aem says it doesnt but you know after a while everything degrades. SO unless you are changing the O2 every year I wouldnt trust it but thats me. me honestly, I think you should not use it.. I mean what are you going to do if you go lean... its another dummy gauge that people say you need but really doesnt do anything for your car unless you are tuning the car yourself and can log it
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Old Yesterday, 07:35 PM   #11
epeder1102
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Quote:
Originally Posted by subaru_gc8 View Post
yeah I dont know about that, I know aem says it doesnt but you know after a while everything degrades. SO unless you are changing the O2 every year I wouldnt trust it but thats me. me honestly, I think you should not use it.. I mean what are you going to do if you go lean... its another dummy gauge that people say you need but really doesnt do anything for your car unless you are tuning the car yourself and can log it
The sensor is literally 3 weeks old.. so it should be good. I installed the gauge because I am hoping to eventually learn and understand datalogs and things so I can step away from the Cobb OTS tunes and try RomRaider for myself.
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