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What I assume is "limp mode" issue

20K views 97 replies 12 participants last post by  Calvinball 
#1 · (Edited)
What I assume is "limp mode" issue. Not solved info in post #1

Ok nothing is solved so let's start fresh.

*new info* Car runs like a champ with MAF unplugged, issues are only with MAF plugged in. MAF and ECM have been replaced, original ECM is back in the car as it saves me $$$

It HAS to be something the MAF is affecting but I can not for the life of me figure out what it is...

Subaru had the car for 3 weeks and the only idea the tech line gave them that they didn't try was oil control valves. *new info*


Ok long story short I flashed Cobb stage 1 and this arose, tried many things and the issue remains.

Car runs perfectly up to 4500 rpm then it just hits a wall, feels like fuel cut or hitting the rev limiter.

2006 wrx tr

I have tried flashing stock map, flashing stage 1 again, completely removed the AP from my ecu.

New plugs
New fuel pump
New fuel filter
New bcs
New MAF
New battery
New MAP sensor
New front O2


Disconnected battery for 12+ hours.
No vacuum leaks of any kind.
Not one CEL.
The problem persists unchanged.

Any ideas from folks wiser than myself?
 
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#38 ·
Assuming throttle V at 3.94 is WOT then it looks like they lifted early. I don't see a wall at all until then. My car has a cable throttle so IDK.

Peak boost is pretty low.

What should you log:

feedback knock correction
fine knock correction
IAM
engine speed
engine load
manifold relative pressure direct
injector duty cycle
wastegate duty cycle
target boost
IAT
mass air flow
Lc-1 (or other wideband) or AFR sensor #1 (factory front O2)
A/F Correction#1 (%)
A/F Learning#1 (%)

http://www.clubwrx.net/forums/tunin...nagement/134322905-datalogging-romraider.html
 
#44 ·
#50 · (Edited)
I'm struggling with how it can run perfectly with the MAF unplugged, but all screwed up once you plug it in. Since the MAF is good, that tells me it's the ECU that is not reading correctly what the MAF is sending it.

Dumb question: Are all of the connections on the MAF plug good where they plug into both the MAF and the wiring harness? (Or maybe it doesn't plug into the harness and the wires from the plug on the MAF run all the way to where they terminate in the main harness, I can't remember.) Any of the wires clipped or frayed or otherwise worn, possibly grounding out?

Could it be a bad 02 sensor feeding bad information back to the MAF, causing it to make inaccurate corrections to the air/fuel ratio?

Maybe a bad EGR valve or some part of that system?
 
#51 · (Edited)
Just brought it home from the mechanic. Yeah the MAF wires look great. Changed the front O2 already. I'm completely out of ideas, I might have to just dump it at Subaru for a while since I've got way too much going on to rip it apart again.

I think I'll make one more run through of hoses and wires tonight though. Maybe something is loose on/near the ECU I dunno.

You guys rock for all the help though, I hope I can repay it someday. :)

Anything I can log that would help?
 
#52 ·
If you changed the front 02 already, then I'd look at the EGR system next. There's not too many things it could be other than this.
 
#56 ·
I have flashed back to the stock map. I've gone back and forth a few times just to be sure.

Also, I checked for leaks 3 or 4 times and the shop had it for a week, they also checked, as did Subaru.

With stage 1 the issue occurs ~3200 RPM, stock ~4500 RPM. MAF disconnected runs like it should.

The dealership can't get to it for about 2 weeks so I'm trying to squeeze in some attempted fixing time between work and mom in the hospital. Not easy.
 
#57 ·
Are you sure the other MAF you tried in it was the correct part number? Or that it wasn't broken?

If all you're changing is whether the MAF is plugged in, then there's really just a few components that could be causing the issue:
MAF - Bad sensor or wiring - See question above
ECU - Bad ECU - possible
02 - Bad sensor - Already replaced, so should be ok.
Piping - Leak - Checked already, so should be ok.
 
#64 ·
That's another code related to all the things you've already reported. It doesn't help diagnose the problem any better, sorry! :(
 
#66 · (Edited)
There's a lot of guys like me and Donkey that are pretty hardcore tuners and car modders so if we can't figure it out, even from internet posts, then you've got a really hard problem. He's stronger on Subarus I bet but I'm probably stronger on a wide bunch of cars. But it just doesn't make any sense. I'd love to see/drive the car in person. That would help me a lot, but that's not going to happen.

Well I take that back maybe I could. I'm heading to Cali some time in the next month or two and passing through your area. :)
 
#68 ·
No, there's no way to test a bad ECU short of swapping it. It's the brains of the operation and runs the show.

Well there is a way to test it but it requires really knowing how to hack an ECU.
 
#72 ·
To the best of my knowledge, yes, all 2.5L engines use the same MAF.
 
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