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Stage 1 Cobb, hesitation and stutter


Chronuss
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  • 2 months later...
So, after waiting for parts from Subaru for seventy thousand years, sending wrong parts back and re-ordering correct ones, them losing one order, going on vacation, I finally got the wagon back yesterday. Drove it home on the stock map, and it feels much better, runs smoother, accel is a bit quicker. Put stage 1 on it...same gods damned ever-loving thing. It hits third gear, AFR jumps to 17-18, goes back to normal. So, can confirm it isn't a mechanical leak of any sort. Used some Google-fu and dug around other forums, so going to try swapping out the front O2 sensor and going to try a new MAF. I don't have reason to believe either one of these parts are actually faulty, but found a few posts in other places with the same conditions I have and others swapped these two sensors out for favorable results, so that is what I will try. Both Denso parts available on the Zon for much less than local auto part stores.
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Does it hit 17-18 and then immediately drop to 11-12? Or does it hit 17-18 and stay there until out of boost?

 

 

 

Stock map works fine?

 

 

 

 

If I drive it in sport mode, it shifts from second to third under boost, AFR hits 17-18, stutters a bit, then comes right back down to 13-14. Cruising at speed its at 14.**, at idle its at 14.**.

 

 

 

Now, if I put it in manual mode, shift from second to third under boost, AFR still hits around 17, but no stutter.

 

 

Stock map feels great, no stutter.

 

 

 

Still waiting on the sensors from Amazon, will be here tomorrow. Long as its not raining, will swap those out real quick and give it a drive. May also try the stage 0 map since its supposed to be "stock," so I can see how it drives with that and see if the AFR does the same thing.

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  • 4 weeks later...
Posted (edited)
Can anyone please tell me the name of this elbow pipe where the front O2 sensor goes? As you can see, the O2 sensor broke off and is completely stripped. I have tried everything to get this thing out. Edited by Chronuss
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Can anyone please tell me the name of this elbow pipe where the front O2 sensor goes? As you can see, the O2 sensor broke off and is completely stripped. I have tried everything to get this thing out.

 

That's part of the exhaust manifold.

https://parts.subaru.com/a/Subaru_2005_Legacy-25L-TURBO-5MT-4WD-GT-Wagon/_54102_6024464/EXHAUST-MANIFOLD-05MY-06MY/B13-055-01.html

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Posted (edited)

This is right before the uppipe on the passenger side, the upstream O2 sensor behind the passenger side wheel well.

 

 

 

So exhaust manifold RIGHT hand side. Thank you. I think its going to be easier to replace that than trying to get this O2 sensor out...that I put in myself...eight years ago. Makes no sense. Thing acts like it was tightened by the right hand of god.

Edited by Chronuss
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I texted you the part number. Not sure if it is still valid.

 

 

 

I should still have my O2 wrenches. I have never had an O2 not come out with some PB Blaster and one of my specialty wrenches. I will check my tool box and let you know. We might be able to extract the broken sensor, it would be all about the threads left in the "bung".

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  • 2 weeks later...

Hint, I put a screw type hose clamp around the O2 socket to keep it from spreading.

305,000miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. CHECK your oil, these cars use it.

 

Engine Build - Click Here

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So my dude got the O2 sensor out...with a ratchet on it...and an air hammer on the ratchet.  Don't know what I did eight years ago under the Florida sun, but damn.

So after the O2 sensor and MAF replacement, still same nonsense when trying stage 1.  I'm over it.  There's no physical air leak so I don't know why the numbers jump.  Runs great stock so that is what she'll do. 

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  • 1 month later...

Sorry to revive this again, but even with the resistor, I keep getting P0420 about once a week.  Since we've now lived through the downfall of Cobb, is Romraider our best choice now to deal with CELs?

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https://www.subaruoutback.org/threads/p0420-diagnosis.49537/

 

Maybe that thread may help with the P0420.  You can reach out to cardoc on here, his name is supercharged.

 

Find him in the March 17th post here, 

 

305,000miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. CHECK your oil, these cars use it.

 

Engine Build - Click Here

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Already replaced the front O2 sensor and the MAF when trying to get the stage 1 Cobb tune to work properly.  Pretty sure the rear O2 sensor just isn't liking the resistor mod.

Even here it is advised to delete this code, but since I can no longer do that with Cobb, was going to try the Romraider approach just to get rid of the code.

 

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On 7/11/2022 at 10:07 AM, Chronuss said:

Thanks all. Got part number, and I'll grab one off ebay if I need to if a torch can't get it out.

Were you talking about the O2 sensor ?

Maybe you didn't know about junk parts from ebay.  I buy parts from trusted places like my local NAPA, Advance Auto Parts, etc. or a few trusted on-line Import Subaru shops. Only use a DENSO 234-9120 front O2 sensor for a 05-07'

Are you buying fake parts?

 
 
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Hopefully your parts are genuine

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305,000miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. CHECK your oil, these cars use it.

 

Engine Build - Click Here

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If your sure you got a really Denso, then I would reach out to "m sprank or cardoc from above. Those two are some of the most knowledgeable guys. 

305,000miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. CHECK your oil, these cars use it.

 

Engine Build - Click Here

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