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IAM at 0, High Fuel Correction, Timing Correction at low load


fox212
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Hi All,

 

I'm having some trouble with my '07 Spec B. Bone stock except for SPT catback.

 

While driving up a fairly steep grade at highway speed (Cuesta Grade, hwy101 for those familiar), I experienced a fairly sudden loss of power. I happened to have BtSSM running at the time and watched the IAM drop from 1.0 down to 0 in under a minute. Pulled a learning view and saw high AF learning down low (16%) and high timing correction at low load (-11.05 deg @ 1.30 g/rev). I also noticed I wasn't hitting target boost (actual was about 3-4 psi below target).

 

Since then, I drove the 15 mi to/from work for a few days, staying out of boost and closely watching AFR values. I parked it once a beater became available.

 

The clutch had been slipping for awhile, so I finally replaced that and tried to keep an eye out for popped vacuum lines, cracks, tears, etc but no dice. I did note a little oil in the I/C outlet but nothing too scary (maybe pointing to PCV though?). Put everything back together to test drive the new clutch - clutch works great, but now the car is even less drive-able. No powah. The slipping clutch must have been hiding the full effect of...whatever is causing my trouble.

 

Throughout all of this - no CEL, no trouble codes.

 

My first thought was obviously a (BIG) vacuum leak, but I've been coming up empty checking the go-to spots. I have not pressurized the intake tract or done any smoke testing yet. Advice on good setups to perform these would be especially valuable, as I think this should be my next step.

 

Attached is the LV from when this first happened.

 

Any help or ideas is much appreciated!

BtSsm_LV_20180317_0940.png.9c9dd6391b686ca5520e5eecfcce45a5.png

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^ Indeed it does! Especially because of how the problem manifested. It "felt" like a hose popped off or something drastic like that. Very sudden.

 

I reset my ECU during the clutch swap and brought the car home yesterday. Very high AFR at idle, but able to hit 14.7 during very light driving. IAM didn't drop during the trip but I was really babying it. Didn't get home until late yesterday, but I popped the IC back off and will hopefully take another look this afternoon for loose or broken vac lines.

 

I have an appointment at a local shop on Thursday, but I'd love to figure out where the problem is myself. I'm told they know turbo Subaru's pretty well but I've never been there before. Options are pretty limited on the central coast, and the local dealership is absurdly expensive for both parts and labor. This one's getting pretty frustrating though!

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Unhook rubber elbow piece from airbox, twist it up and plug hole with aerosol can lid. Pull off small hose on top of intercooler, and blow into it then put thumb over it. If you have an obvious leak you should be able to hear it easily when you are blowing.

 

Granted I haven't done this for a year, but i'm pretty sure that's the sequence - used it many times with success.

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I havent had any issues since I zip tied all of the connections. Have you checked the small hose just above the injectors on the passenger side that plugs into the intake manifold? My next bet would be the T under the IC, or the IC to intake connector.
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Thanks Matt166. I'll definitely try the breath test as I do think it's a very big leak. I can definitely hear it when I'm driving near a wall or building and just starting to spool the turbo.

 

When you say small hose on top of intercooler, do you mean one of the BPV hoses?

 

IIRC, 2007+ don't have the blue T under the IC.

 

I did check both turbo-IC and IC-throttle body connections, didn't see any obvious damage. Didn't really get a good look at the turbo inlet-turbo clamp area, which I know is a fairly common problem spot.

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Thanks Matt166. I'll definitely try the breath test as I do think it's a very big leak. I can definitely hear it when I'm driving near a wall or building and just starting to spool the turbo.

 

When you say small hose on top of intercooler, do you mean one of the BPV hoses?

 

IIRC, 2007+ don't have the blue T under the IC.

 

I did check both turbo-IC and IC-throttle body connections, didn't see any obvious damage. Didn't really get a good look at the turbo inlet-turbo clamp area, which I know is a fairly common problem spot.

 

Correct, the small hose (BPV pressure reference) is the one you want. Also correct, no blue tee on the '07+.

 

Definitely looks like a vacuum leak. Try the blow-into-the-hose test first, since it's quick and easy.

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Thanks, Gents!

 

I'll do the breath test and re-check the TMIC-to-TB. I did just have the TMIC off for the clutch swap, and it looked intact. Re-seated and clamped down just fine as far as I could tell. Maybe I need some smoke and/or good light to see if that hose is just punctured somewhere??

Edited by fox212
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For a leak this big, you may have success with a spray test. With the engine idling, prop up your BtSsm device on a shock tower or whatever and display the fuel correction gauge. Spray propane, brake cleaner, starting spray, or some similar volatile combustible around the typical problem spots. If the combustible gets into the post-MAF airflow, the fuel correction (STFT) value will drop sharply. Although your idle trim is clearly so far off the scale it may never drop low enough for you to see it (<15%).
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Found it!

 

I capped the intake and pulled the BPV pressure reference line off the BPV, and guess what...it was the other end of that line :lol: Upon first inspection it looked like it was on the nipple, but I guess it was just sitting right in front of it :spin: Went ahead and zip-tied that biotch on both ends.

 

Fuel correction at idle immediately went to 0, and the others are shaping up quickly as of this morning. IAM is staying at 1 and there are no timing corrections across the board. So I'm gonna say problem solved. :cool:

 

Thank you all for your help!!

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