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Old 05-14-2013, 12:23 PM   #1
BeastianSTI
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Default MAF / O2 Sensor voltages

Hey guys,

I've got an 05 STI with:
- TGV Deletes
- APS TIP
- APS CAI
- TMIC

The car was protuned with all of these mods installed.

I'm having an issue where my car is running very rich in boost, and i'm trying to track down why. My AF stored values (from LV) are very low.

I replaced the Front o2 sensor, and now i'm turning my eye towards the MAF sensor... I noticed the voltage levels in this log; are these normal for the MAF and o2 sensor?

When I took it to the dealership to get the Subaru select on it, I told them it was running rich. They said that it seemed like somewhat erratic o2 sensor readings (voltage?).

https://docs.google.com/file/d/0B0i3...it?usp=sharing

Thank you guys!
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Old 05-14-2013, 01:25 PM   #2
the suicidal eggroll
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How do you know it's running rich in boost?

When you're in boost the system is in open loop, so other than the learned fueling adjustment the O2 is having no effect. If the AFR Learning looks normal, the O2 sensor cannot cause a fueling problem in open loop.
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Old 05-14-2013, 02:37 PM   #3
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Originally Posted by the suicidal eggroll View Post
How do you know it's running rich in boost?

When you're in boost the system is in open loop, so other than the learned fueling adjustment the O2 is having no effect. If the AFR Learning looks normal, the O2 sensor cannot cause a fueling problem in open loop.
Dang - that's some good information. My wideband is telling me that i'm running really rich -- 9.8 at WOT.

I cleaned the MAF sensor, and it changed how the car ran. My A/F Learning stored sorted itself out, but I was still running super rich.

So what are the only possible causes at this point?
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Old 05-14-2013, 03:08 PM   #4
the suicidal eggroll
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Well make sure your AFR Learning is in good shape, since this is calculated and modified in closed loop, but is still carried over and applied in open loop. Generally less than 3% is considered good.

Beyond that, a bad MAF, bad MAF scaling, or boost leaks are the main causes for running rich in boost.
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Old 05-14-2013, 03:21 PM   #5
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It was at about 6% for A, and 3% at C, but there aren't any boost leaks (multiple boost / smoke tests confirm), and no mods have done since it was tuned (added Walbro LPH 255 pump, however).

I suppose it has to be the MAF sensor then. Could FPR have anything to do with this?
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Old 05-14-2013, 03:26 PM   #6
the suicidal eggroll
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When did the rich business start? The fuel pump could be the culprit.

Usually a fuel pump change won't cause this, BUT you were professionally tuned before you got it. The tuner could have easily been compensating for a drop in fuel pressure from the insufficient pump by jacking up the MAF scaling. Now that the fuel pressure problem has been fixed with the new pump, that MAF scaling adjustment would now be making you run too rich.
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Old 05-14-2013, 03:51 PM   #7
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Not sure. I installed the FP about 8 months ago, as recommended by my tuner. At that time he said i shouldn't need a re-tune for it.

Car has been down on power for almost a year, but I got a wideband a couple of months ago, and noticed it was just dumping fuel. Started really trying to get to the bottom of it recently.
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Old 05-15-2013, 06:44 PM   #8
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Anything I can do to confirm this?? Or test the maf maybe?
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Old 05-15-2013, 07:10 PM   #9
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Anything I can do to confirm this?? Or test the maf maybe?
Maybe they just tuned it for that rich... What did your tuner say?
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Old 05-16-2013, 11:43 AM   #10
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He said it was way too rich, but wasn't able to really help me diagnose the issue.
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Old 05-16-2013, 12:29 PM   #11
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Did he experiment with tweaking maf scaling at all to see if it helped?

Steve @ Pullz-On Tuning
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Old 05-16-2013, 04:10 PM   #12
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No, he actually retired from tuning, unfortunately.
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Old 05-16-2013, 04:21 PM   #13
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OP, I did notice that your AF learning A range was as high as 7% at idle. You could have a bad o-ring at the maf sensor causing a a vacuum leak which you would not have discovered leak testing. You also didn't say what AF learning D was which can get carried over and applied in OL unless your tuner effectively turned that off. If AF learning D is still enabled and positive it could be making you richer.
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Old 05-16-2013, 04:25 PM   #14
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No, he actually retired from tuning, unfortunately.

Where in Florida are you located? I'm headed down there in a couple weeks on vacation and would rather be behind a laptop in a Subaru then on the beach.. lol

Steve @ Pullz-On Tuning
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Old 05-16-2013, 04:59 PM   #15
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Originally Posted by nmlittlebigman View Post
OP, I did notice that your AF learning A range was as high as 7% at idle. You could have a bad o-ring at the maf sensor causing a a vacuum leak which you would not have discovered leak testing. You also didn't say what AF learning D was which can get carried over and applied in OL unless your tuner effectively turned that off. If AF learning D is still enabled and positive it could be making you richer.
A = 6.20
B = -0.5
C = 3.40
D = 0

and we replaced the o-ring with another type of o-ring, but the actual plastic that holds the o ring was deteriorating.


I'm located in Lutz / Tampa!
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Old 05-16-2013, 05:19 PM   #16
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Quote:
Originally Posted by BeastianSTI View Post
A = 6.20
B = -0.5
C = 3.40
D = 0

and we replaced the o-ring with another type of o-ring, but the actual plastic that holds the o ring was deteriorating.


I'm located in Lutz / Tampa!
I'll be in the panhandle

What size APS intake?

Steve @ Pullz-On Tuning
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Old 05-16-2013, 05:40 PM   #17
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The APS Intake has a 3" diameter
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Old 05-16-2013, 05:46 PM   #18
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I was gonna say, I have a local car I recently did with a 70mm APS intake and I could compare the MAF scaling to see if your tuner was compensating for a bad fuel pump with the MAF scaling....

Steve @ Pullz-On TUning
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Old 05-16-2013, 05:54 PM   #19
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Actually - I think it is 70mm, come to think of it. What do you need to see? The ROM?
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Old 05-17-2013, 01:04 AM   #20
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Hey guys, I took some logs today and was increasing the IAM, and caught the IAM dropping in the log from .75 to .625~. I don't really see anything causing knock etc, or fueling issues that caused the drop. I also noted that the Fine learned knock tables had 0's all across the board.

What do you guys think? What else am I missing?

https://docs.google.com/file/d/0B0i3C9x11ZNVZGU2azV2Z0ZwNlk/edit?usp=sharing[/url]

Last edited by BeastianSTI; 05-17-2013 at 09:10 AM.
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Old 05-17-2013, 08:24 AM   #21
nmlittlebigman
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Quote:
Originally Posted by BeastianSTI View Post
Hey guys, I took some logs today and was increasing the IAM, and caught the IAM dropping in the log from .75 to .625~. I don't really see anything causing knock etc, or fueling issues that caused the drop. I also noted that the Fine learned knock tables had 0's all across the board.

What do you guys think? What else am I missing?

https://docs.google.com/file/d/0B0i3C9x11ZNVZGU2azV2Z0ZwNlk/edit?usp=sharing
Your link doesn't work. In general though right after a reflash your ecu goes into rough correction mode (FLKC is not enabled yet) until the IAM settles in. If your IAM is dropping then your knock sensor is detecting knock (or something it thinks is knock).
See: http://www.romraider.com/forum/topic1840.html
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Old 05-17-2013, 08:39 AM   #22
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Quote:
Originally Posted by BeastianSTI View Post
Actually - I think it is 70mm, come to think of it. What do you need to see? The ROM?

Yea. Email it to me.
boostaddict79@gmail.com

Steve @ Pullz-On Tuning
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Old 05-17-2013, 09:05 AM   #23
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Old 05-17-2013, 09:22 AM   #24
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Quote:
Originally Posted by BeastianSTI View Post
Your car is NOT happy. Definitely get a tune ASAP. You had some massive knock and it appears that the tune on your car has some workarounds like disabling AF learning above 1100 RPM. If I were in your shoes I would have Steve tune it. I hear nothing but good things about him.
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Old 05-17-2013, 09:29 AM   #25
BeastianSTI
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Quote:
Originally Posted by nmlittlebigman View Post
Your link doesn't work. In general though right after a reflash your ecu goes into rough correction mode (FLKC is not enabled yet) until the IAM settles in. If your IAM is dropping then your knock sensor is detecting knock (or something it thinks is knock).
See: http://www.romraider.com/forum/topic1840.html
Yeah, I didn't thoroughly look at that portion of the log. I was doing the Vishnu reset, and looks like it picked up knock ..

Last edited by BeastianSTI; 05-17-2013 at 09:34 AM.
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