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Old 06-14-2013, 01:37 AM   #1
iNfEk
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Default MAF Sensors

My understanding and cross referencing of MAF sensors for 02-07 WRX & STI should be the same. This is also confirmed via Denso's website as well (197-6040) for both 2.0L & 2.5L including EJ205 and EJ257.

This is for a JDM EJ207 that uses the same MAF for a EJ205.

I ordered a Denso MAF because my 12 year old MAF that I've had on my 2002 WRX was hitting higher than the allotted range on my MAF table set by my tuner years ago. This caused problems where my car started to buck when trying to boost or going WOT.

I swapped sensors with a friend from a 2005 STI (p/n: 22680AA310 -- 197400-2090 (Denso)) and the car ran smooth like butter again.

GREAT! Since my replacement sensor was on its way.

Today I receive that MAF (Denso 197-6040) and put it in. My car immediately starts bucking and acting the same way it did previously with my OLD MAF. Put back the STI one and the car runs great!

Obviously this is the problem.

On my old MAF the load points were hitting 2.95 when the MAF table was max 2.80. My understanding is the ECU didn't know what to do with the additional air readings so it creates a rich condition at the point of boost. Boost still gets created so no pressure leaks or vacuum leaks are present.

I haven't logged this event with the new MAF but did reset the ECU before installing the new MAF.

What is the difference and why would the MAF from my friends 05 STI work flawlessly whereas a BRAND NEW SEALED IN PACKAGE AND BOX wouldn't?

I understand I could probably rescale the MAF table but this setup as been running for years like this with only the trouble happening recently (last week). Why would this occur?

Since the 05 STI owner uses MAP instead of MAF he is using my "bad" MAF for the temp sensor only. I can't verify my part number at this time. I have a friend with a 2002 WRX that has the same MAF part number as my friends STI.
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Old 06-14-2013, 02:14 AM   #2
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Just confirmed that my old sensor, my friends bugeye and the STI owners MAF is the same part number 22680aa310

Is it safe to say bad DENSO replacement MAF?

Is there actually a difference between the denso version and the oem Subaru version even though they're made by the same company?
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Old 06-14-2013, 09:35 AM   #3
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Since it is a different part (perhaps for retail use), the Denso calibration is set differently to fit a broader set of vehicles than the OEM 19400-2090 Denso part number.

One way to test the theory is to test the 6040 in a stock subaru and see if the ecu adjusts accordingly and acts smooth. This will rule out any other modifications that may contribute to your bucking experience.
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Old 06-14-2013, 12:00 PM   #4
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Quote:
Originally Posted by fastnoypi View Post
Since it is a different part (perhaps for retail use), the Denso calibration is set differently to fit a broader set of vehicles than the OEM 19400-2090 Denso part number.

One way to test the theory is to test the 6040 in a stock subaru and see if the ecu adjusts accordingly and acts smooth. This will rule out any other modifications that may contribute to your bucking experience.
Thanks. I haven't changed anything other than the MAF and what was mentioned in the 207 thread. After the change out of said item immediate night and day difference.

I appreciate the suggestion but getting the car back to running conditions before my expected tune is kind of important.

I plan on going to the dealer today to purchase one. If my friend has time we can experiment before I'm required to return the MAF to amazon.
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Old 06-14-2013, 01:53 PM   #5
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i hear you, sometimes it eats up more of your time to seek alternatives than use the OEM parts that are known to work right the first time. Good luck!
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Old 06-14-2013, 02:01 PM   #6
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What do you mean it was hitting 2.95 when it was calibrated for 2.80. Do you mean voltage? I'm guessing that at idle it's bounces from 2.80 +\- a few. Do you have a cobb? You can try cleaning the old maf and see if that helps.
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Old 06-14-2013, 02:06 PM   #7
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Quote:
Originally Posted by fastnoypi View Post
i hear you, sometimes it eats up more of your time to seek alternatives than use the OEM parts that are known to work right the first time. Good luck!
Thanks homie. It was cost.

Quote:
Originally Posted by Ryan321 View Post
What do you mean it was hitting 2.95 when it was calibrated for 2.80. Do you mean voltage? I'm guessing that at idle it's bounces from 2.80 +\- a few. Do you have a cobb? You can try cleaning the old maf and see if that helps.
Calculated load point values in the ECU. Cleaning did nothing. It 12 years old but anything shooting over the voltage limit the ECU doesn't know what to do with it so bucking and rich condition happens even though boost gets generated.

I've done a lot of research prior to this thread to determine the MAF is the culprit.

A brand new MAF (oem replacement) made by denso shouldn't have this issue though.

Last edited by iNfEk; 06-14-2013 at 05:26 PM.
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Old 06-14-2013, 04:47 PM   #8
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Just bought OEM =\


Hope it works!
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Old 06-14-2013, 06:22 PM   #9
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*drum roll please......*
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Old 06-14-2013, 06:30 PM   #10
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*drum roll please......*
LOL. won't know till after work today. Ill post.
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Old 06-14-2013, 10:52 PM   #11
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Doesn't work either. =\ idk. Maybe the tune needs adjusting. Doesn't seem logical at this point.

I can't understand why this is happening and there is no logical reasoning to the problem.
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Old 06-15-2013, 12:36 AM   #12
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does the new maf work in your buddys sti? if it does it may be your tune???
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Old 06-15-2013, 12:43 AM   #13
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does the new maf work in your buddys sti? if it does it may be your tune???
Thanks. My buddies STI doesn't use MAF but utilizes MAP instead. He uses the MAF only for the temp sensor so it wouldn't make a difference. Tomorrow we are going to check the voltage readings on the 4 MAF we have:

New Subaru OEM MAF
New DENSO OEM equivalent MAF
05 STI MAF (current one that allows my car to boost)
OLD WRX MAF

The company tuning my car has been contacted since they're going to be coming down in July. I hope he has some suggestions on the issue.

Yeah I considered this might be the issue.
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Old 06-15-2013, 12:59 AM   #14
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Quote:
Originally Posted by iNfEk View Post
Doesn't work either. =\ idk. Maybe the tune needs adjusting. Doesn't seem logical at this point.

I can't understand why this is happening and there is no logical reasoning to the problem.
Nothing has changed pre/post MAF other than the turbos compressor gasket you found leaking?

(I try to pay attention)

I know you live in a very controlled climate, so corrosion most likely isn't a problem. How does the lead and connector look?

Seems real funky that 1 of 4 works just fine.... If none of them worked, then duh, the tune is to blame. Which has been unchanged in how long?

Then again, if it were tuned with that turbo leaking, now more air is being metered by the MAF, hence voltage spike. Then ya, the tune needs tweaking.

Just my .02 :-)
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Old 06-15-2013, 01:10 AM   #15
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Originally Posted by projectQWKSLVR View Post

Nothing has changed pre/post MAF other than the turbos compressor gasket you found leaking?

(I try to pay attention)

I know you live in a very controlled climate, so corrosion most likely isn't a problem. How does the lead and connector look?

Seems real funky that 1 of 4 works just fine.... If none of them worked, then duh, the tune is to blame. Which has been unchanged in how long?

Then again, if it were tuned with that turbo leaking, now more air is being metered by the MAF, hence voltage spike. Then ya, the tune needs tweaking.

Just my .02 :-)
Right. As of right now nothing. Gonna check that tomorrow too again just to quadruple check again.

No corrosion of any kind.

I tightened the bolts I could to the compressor housing and didnt see a leak anymore. But gonna check again as stated earlier.

The tune has been running for at least 3-4 years now. That's definitely true about the unmetered air. However if that were the case. Why would 1 of 4 MAF sensors work fine? It wasn't the one used to originally road and dyno tune the car years ago.

We will look over the voltage stuff of the 4 sensors tomorrow and see if the voltage readings are different. If they are. They aren't the same sensors even though they have the same part number.
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Old 06-15-2013, 01:18 AM   #16
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Quote:
Originally Posted by iNfEk View Post

Right. As of right now nothing. Gonna check that tomorrow too again just to quadruple check again.

No corrosion of any kind.

I tightened the bolts I could to the compressor housing and didnt see a leak anymore. But gonna check again as stated earlier.

The tune has been running for at least 3-4 years now. That's definitely true about the unmetered air. However if that were the case. Why would 1 of 4 MAF sensors work fine? It wasn't the one used to originally road and dyno tune the car years ago.

We will look over the voltage stuff of the 4 sensors tomorrow and see if the voltage readings are different. If they are. They aren't the same sensors even though they have the same part number.
That's what's boggled the mind. Why 1 of 4? That's what triggered the connection point as a possible suspect. I doubt the o-ring on the sensors is to blame.

When swapping sensors, are you resetting the ecu/ removing neg terminal from batt? The datalogs should show "real" voltage, not any kind of stored/ learned value though, so that shouldn't have any effect. Knowing you are thorough I imagine each swap was an identical process.

I'm interested to see what's up with this. I'll be sure to remember when choosing a replacement MAF sensor!
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Old 06-15-2013, 01:30 AM   #17
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Originally Posted by projectQWKSLVR View Post

That's what's boggled the mind. Why 1 of 4? That's what triggered the connection point as a possible suspect. I doubt the o-ring on the sensors is to blame.

When swapping sensors, are you resetting the ecu/ removing neg terminal from batt? The datalogs should show "real" voltage, not any kind of stored/ learned value though, so that shouldn't have any effect. Knowing you are thorough I imagine each swap was an identical process.

I'm interested to see what's up with this. I'll be sure to remember when choosing a replacement MAF sensor!
New sensors. ECU was reset. Old. No. But it's night and day feel. AFR readings are different too at idle.

Literally I do a ECU reset then put new MAF. Idle for a little bit then drive normal above 10% throttle car starts bucking or gets rich bogs before boost. Take out that new MAF. Put 05 STI one and its fine. I don't own a windows laptop anymore so can't log or check.

The denso MAF bucks. Subaru bogs. Both conditions no cel and boost is increasing.

Oh. Ran the working MAF today. Got home took it off and the O ring breaks off. I swap with new and bogging happens. Put that other MAF on without o ring and its fine.
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Old 06-15-2013, 01:41 AM   #18
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Quote:
Originally Posted by iNfEk View Post

New sensors. ECU was reset. Old. No. But it's night and day feel. AFR readings are different too at idle.

Literally I do a ECU reset then put new MAF. Idle for a little bit then drive normal above 10% throttle car starts bucking or gets rich bogs before boost. Take out that new MAF. Put 05 STI one and its fine. I don't own a windows laptop anymore so can't log or check.

The denso MAF bucks. Subaru bogs. Both conditions no cel and boost is increasing.

Oh. Ran the working MAF today. Got home took it off and the O ring breaks off. I swap with new and bogging happens. Put that other MAF on without o ring and its fine.
Hmm... So it wants to leak? Stock box and MAF housing?

Makes me think tune again, due to it running properly with a leak. As if it were tuned rich to compensate for the leak. Take leak away, now it dumps even more fuel, to the point of washing out the spark at low loads.
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Old 06-15-2013, 01:59 AM   #19
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Originally Posted by projectQWKSLVR View Post

Hmm... So it wants to leak? Stock box and MAF housing?

Makes me think tune again, due to it running properly with a leak. As if it were tuned rich to compensate for the leak. Take leak away, now it dumps even more fuel, to the point of washing out the spark at low loads.
No. APS CAI 65. it was tuned with it on. The sensor hole is tight with the o ring so it kills the ring. It's pretty snug without the ring though.

It's like shooting in the dark at this point. All logic is out the window LOL
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Old 06-15-2013, 06:14 AM   #20
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So you have 4 mafs.
2 new ones.
One bad one.
1 from an STI. sti works great. 2 new ones don't. What mods are you tuned for right now ? I suspect that the sti maf scaling is different than the wrx scaling. If you were tuned for certain mods and airflow than a brand new maf will still need adjusting.
Side note. O ring size 32mm o.d 28 mm I.d by 2mm.
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Old 06-15-2013, 09:19 AM   #21
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it would be nice if you were able to log the maf voltage at idle, maybe borrow a windows laptop and log it. that along with logging long term fueling and short term fueling to see how they are doing
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Old 06-15-2013, 02:10 PM   #22
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Originally Posted by WrxWrb View Post
So you have 4 mafs.
2 new ones.
One bad one.
1 from an STI. sti works great. 2 new ones don't. What mods are you tuned for right now ? I suspect that the sti maf scaling is different than the wrx scaling. If you were tuned for certain mods and airflow than a brand new maf will still need adjusting.
Side note. O ring size 32mm o.d 28 mm I.d by 2mm.
The STI MAF is the same exact part number. I thought that too but since its the same part number it can't be different. Thanks for the o ring size.

EJ207 92 octane
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the only difference is I corrected some hoses that goes back into the crank case and my AOS so air flow isn't restricted like it was previously (slightly collapsed hose).


EDIT: maybe the "bad" MAF actually isn't bad at all since the new MAF sensors act the same way.

Quote:
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it would be nice if you were able to log the maf voltage at idle, maybe borrow a windows laptop and log it. that along with logging long term fueling and short term fueling to see how they are doing
Yes that's what I plan on doing today with a friend. We plan on seeing exactly how the voltage levels and spikes (if different) to determine if they're exactly the same sensors or not even if they have the same part number. I'm open sourced tuned but my friend isn't so experienced with tuning. Don't really want to touch stuff before my tuner gets here. I was looking on rom raider website and they mentioned "MAF TOOL" where it can scale your MAF for you??? Did I read this incorrectly?

It is possible that when I tuned my car years ago that the MAF scaling was adjusted for an old MAF readings rather than that of a "good" one.

The problem with tuners is that unless you have a perfectly running car before the tune most don't care and will say can't tune because of a mechanical issue. Which I find to be bull****. I don't care how good of a tuner you are. If you over book and can't help resolve due to your lack of customer service skills then you're no skilled tuner. Period.

I'm trying to resolve issues at least a month a head of a tune that I've NEVER had with this car nor with this engine. I honestly haven't ever had issues with this setup till recently.

I appreciate the suggestions.

Last edited by iNfEk; 06-15-2013 at 03:22 PM.
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Old 06-16-2013, 03:19 AM   #23
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Or.. keep your buddies '05 STI MAF and give him one of the 4 others you have to read temp for him.
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Old 06-19-2013, 05:14 PM   #24
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Ummm that's not an option since it's still an old MAF and if my car were stock what would subaru do if this situation came about when they determine a MAF to be faulty or out of specifications. It baffles me that a simple changing of a MAF to a new one can make a car that has ran perfectly for at least 3 years on this EWG setup and only now this is happening.

any way...

did some logs to compare the new subaru MAF and the "working" MAF and i get pig rich around the time boost gets created with the subaru MAF (similar to the denso one as well). Boost continues to build but bucking happens. The "working" MAF has -8% correction whereas the subaru MAF shows -13% correction.

I will say though that the AFRs are different between the different MAFs and that even though the subaru MAF won't allow me to boost properly but the car drives pretty good down low before boost. again partial throttle allows me to avoid bucking issues which is quite lame.

With the subaru MAF I only reach about 50% throttle before bucking happens where a rich condition of 9.75 AFR as present. With the "working" MAF I can go go well beyond that throttle percentage and AFR dips rich then goes back towards normal.

I have contacted AMS to find out what they think about it.

A friend of mine did adjust the MAF scaling slightly for the subaru maf to account for -10% correction and the car did seem to do a little better. I don't want to change too much since my tuner is looking at the log files we took while driving normally and trying to reach WOT with both MAFs.

I'll still continue to see if I can locate any additional SMALL leaks that might be contributing but this is a very "ODD" problem. I hope this **** gets resolved soon. I won't be buying any additional parts unless there is a definitive reason to.

EDIT: I did ask my tuner if its MAF Scaling and/or fuel trim. Didn't get a response. But he did say "Im not worried then, it should tune out just fine"

Last edited by iNfEk; 06-19-2013 at 05:43 PM.
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Old 06-29-2013, 12:20 AM   #25
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replace o-ring on said MAF? I know this will cause problems on occasion
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