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2009 Outback XT (5MT)
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Discussion Starter #1
Been working at this for the past couple of days, which is as long as I've owned the car. Car is an 09, 124k, 5MT, freshly rebuilt engine, all stock as far as I can tell. Picked it up in Denver and drove it back to San Antonio.
When I first got it, the car was producing ~14psi and power deliver was good, nice and even, once I was over 3000rpm. The farther I drove the higher my fuel trims rose.... Until I finally got a p0171 (system too lean). Took a look under the hood and found a couple of loose lines, as well as a torn one. Vac line on the bottom of the T was off, and the short piece of vac line on the left of the T (with the restrictor pill) was torn. I cut the torn part off, but the line was too short to have the pill in it now, so I dropped it in the center console for later and ran the line without it. Fuel trims improved, code did not come back. Turbo spooled much quicker, but boost peaked at 10psi. Power delivery felt better regardless, but fuel economy dropped significantly. I never did find a place that had vac line in stock (most of the drive was overnight) so I got all the way home like this.
Yesterday I replaced the vac line and reinstalled the pill. Turbo spool improved yet again, and produced 16+psi (more than it should stock AFAIK) but the car felt like it was missing or somehow hesitating at WOT. Part throttle acceleration feels smooth and overall much more powerful than WOT. Fuel economy came back.
Today I opened the hood and inspected the engine from every possible angle and finally found a larger hose in front of the TMIC was disconnected at the elbow. (PCV?) Got it reconnected and the WOT issue diminished by about half, but it is still present. Peak boost is now 15psi, and part throttle acceleration still feels slightly better than WOT.
No codes since the p0171 which was 700+ miles ago now.
Ii have also noticed a slight vibration at idle.
I've been searching through as many similar posts as I can find. Haven't found a situation described exactly as mine but those that are similar have found the answer to be:
plug(s) (replaced during rebuild. 1000mi on them)
coil pack
vac leak
MAF (one I have appears to be new, but aftermarket)
Wastegate
O2/AFR sensors
What else?

General consensus across many threads is, a datalog is required to really find out what's going on here... I have an OP 2.0, and have logged, but don't have a good solution for parsing so much data. All I have is a win10 tablet right now and there is just way too much data for a screen that size. I also don't really know exactly which datapoints I should be logging, and what the data should look like when everything is working properly. I'm a fairly adept DIY mechanic but this is my first Subaru and first boosted car so there's a lot of "new" I'm trying to take in.
If anyone has any suggestions on what parameters I should log and what to look for in those logs, the help would be greatly appreciated.
 

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Outback 2011 3.6R Premium
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1,341 Posts
If you have everything else sorted out (vacuum leak etc) I would be adding some good quality injector cleaner to the system and see if that helps.

I am suspecting your injectors might not be delivering a “full shot” at WOT.

Seagrass
 

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05 GT wagon, 09 Spec B, 18 3.6R Outback
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484 Posts
Having a LGT for 16 years, lot's of us feel the car is better at 7/8 throttle then WOT. Also if its hot outside, performance will drop a little.

As he said ^ you'll want to check out that forum.
 

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Having a LGT for 16 years, lot's of us feel the car is better at 7/8 throttle then WOT. Also if its hot outside, performance will drop a little.

As he said ^ you'll want to check out that forum.
Now that you mention it my LGT felt that way as well, but I learned to enjoy finding that sweet spot on the throttle.
 

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I bought my used 06 XT - and when I needed to replace the turbo I did it engine-out.

I found boost leaks, loose hoses at the intake manifold, loose intercooler piping.

you should also verify the thin hose from the manifold to the fuel pressure regulator is there and good.

your 10lbs of boost may also be a good car refusing to run harder in hot weather, due to knock.

until you're comfortable that's the case, look for boost leaks, plural.
 

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2009 Outback XT (5MT)
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Discussion Starter #7
@seagrass I suspected the same, and did dump a full 16oz of seafoam into the tank before my second fill up on the way home. Given I was still working out other issues at the same time, can't really tell if it helped. I may do it again, with only a half tank of gas.

@SilverOnyx I have been doing a ton of reading on LGT. I have an account there as well but haven't used it much yet due to the site not being very mobile friendly. There is definitely a much larger amount of material there to sift through thou.

@Max Capacity Better at 7/8, this is fairly accurate. Maybe what I am feeling is normal after all then. I know heat takes it's toll... That's in every car. Saturday morning close to home it was ~75F out, and even with no restrictor pill, other leaks and only making 11psi, that's the most powerful it's felt so far. Most of my driving is now happening when it's 90-105F out, making 15+psi but not pulling as hard as it was while it was cool.

@S.O.B.06xt I have gone over every hose I can see... and a few I can only feel. I'm mostly certain things are buckled down now. 10psi was at night when things were below 90F, and I still had leaks, and no restrictor pill. Now pushing 15-16psi in full South TX heat on 93 octane. Logged for 15min yesterday and only got two counts of knock.

I decided to reset the ECU this morning before going out for a drive (you'd think I'd have thought of this sooner). After driving the car from 4000+ft elevation with a handful of boost leaks and open PCV line, down to 600ft elevation and fixing all those leaks (I think), I figured maybe the problem was now just the learned behaviours which were previously compensating for said leaks and elevation. The car feels better than it did yesterday. There is still some uneven power delivery at WOT but it is even less pronounced than yesterday. There is still a small amount of vibration at idle.
Still making 15-16psi in 100F heat... Which is more than I expect honestly. Isn't this thing supposed to make 13.5 +/-1 when stock?
I wonder if it's been reflashed by a previous owner... Or if I have a wastegate issue?

Thanks all for your help!
 

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2009 Outback XT (5MT)
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Discussion Starter #8
The MAF in the car is a spectra ma234. Sold at advanced auto for $117, amazon for $70, and rockauto for $36... Lol. Not trusting a $36 aftermarket MAF for anything. Denso 197-6130 is headed to my mailbox. Even if it doesn't change anything... I'll feel better in the long run with an OEM MAF sensor.
 

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My 0.0002 on a possible wastegate issue is if the boost isn't generally bouncing around or spiking as revs rise in the higher gears, it's working at whatever boost it's set to.

I.e. it's generally working. ?!
 

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2009 Outback XT (5MT)
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Discussion Starter #10 (Edited)
No increase in boost as revs rise. After watching closer it appears the peak numbers I am seeing are just an initial spike 1-2 seconds after I put my foot down, then it holds 13-14psi after.
Still feeling some hesitation in heavy part throttle and WOT, especially above 4500rpm. The higher the rpm the more likely the hesitation is. Hoping the new MAF will help... If not then I guess plugs, coils and injectors are the next suspects.
 

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2009 Outback XT (5MT)
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Discussion Starter #11
Welp.... Lesson learned. When cross-referencing part numbers: double, triple and quadruple check before ordering.
Denso 197-6130 is for the NA engine. Thankfully the MAF sensor I ordered was so different I noticed before opening the bag, so it can still be returned.
Regardless of what some Amazon sellers may tell you, 197-6130 is not for the XT! After verifying with multiple sources, I now have Denso 197-6040 on its way to me. Hope I get it tomorrow.
I dumped seafoam in the tank again. Twice as much as before. It seems to have helped some but the issue is still present.
Fuel economy is considerably lower than I expect as well. This week I've been doing mostly highway driving, with very little idle time. I do use "S#" when leaving from a stop, or to pass, but otherwise in "I" and cruise control everywhere else. Still at 19.5mpg. Somehow worse than the initial drive home, with all the boost leaks, no restrictor pill, lower octane fuel, speeding and staying in "S" or "S#".
I don't get it. Sure hope it's the crappy aftermarket MAF.
 

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2005 OBXT Limited, VF37, STI intake, 5MT
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I'd also confirm the turbo that's in there. Should be a VF46, many people use a VF52 as an upgrade (or VF40 as a cheap/easy replacement).

Restrictor pill should be in place, and I'd also check that the boost control solenoid is connected correctly and free.

There are some nice add-ons for Excel to handle CSVs with the multiple lines of data. Some paid standalone programs too.
 

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2009 Outback XT (5MT)
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Discussion Starter #14
@S.O.B.06xt yes the OEM scoop is there. Air filter is brand new and I just got the new MAF today. Installed it, reset ECU and let it warm up to operating temp from a cold start. Will drive tomorrow... Fingers crossed. The aftermarket MAF looks pretty different from the Denso so I expect a difference. Previous MAF read ~2.6g/s at idle, Denso MAF ~3.2g/s... Still some vibration at idle thou.

@RoughDiamond It probably wouldn't hurt to check the turbo out. Would be a pleasant surprise (in the long run) if it were a VF52, but I think it's much more likely it was replaced with a VF40 if it isn't the original VF46.
Restrictor pill is in place, left side of the T. Will see if I can find some diagrams of the BCS, but everything looks ok as far as I can tell.
 

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2009 Outback XT (5MT)
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Discussion Starter #15
I'm fairy certain this is completely resolved with the new MAF. Power delivery is night and day. No more stuttering, top end has some power now. Highway fuel economy jumped from 19.5mpg to 28.6! What a difference.
 

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2009 Subaru Outback XT. AT
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I'm fairy certain this is completely resolved with the new MAF. Power delivery is night and day. No more stuttering, top end has some power now. Highway fuel economy jumped from 19.5mpg to 28.6! What a difference.
My .2 cents: these cars a very finicky. One time I was experiencing similar issue and I noticed the o ring on the dip stick was worn. I simply wrapped it with black electrical tape and instantly my mpg’s went up and car became more responsive. Prior to this easy fix it felt like the car was running with a bad pcv.
 

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2009 Outback XT (5MT)
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Discussion Starter #17
On that note... Can anyone tell me what vacuum numbers should be like at idle, and cruising near 3000 rpm on flat road? I'd like to have some confirmation everything is right. Feeling like it's 95% there but still feel the slightest bit of stutter sometimes, after getting past turbo lag.
It may just be the heat. Consistent upper 90s, if not over 100 around here. Won't know if that's it for at least two more months.
 

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I seem to remember a car/driver review of the gen3 turbo outback ... Reported some irregularities in the throttle response.

Could also be light detonation. If you're a masochist you can try plugs 1 range colder than stock ... Then again, if your MAF was for a normally aspirated car so could be your plugs.

... Turbo plugs are gapped smaller. That'd do it too.
mmmv,
M.
 

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2009 Outback XT (5MT)
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Discussion Starter #19
I seem to remember a car/driver review of the gen3 turbo outback ... Reported some irregularities in the throttle response.

Could also be light detonation. If you're a masochist you can try plugs 1 range colder than stock ... Then again, if your MAF was for a normally aspirated car so could be your plugs.

... Turbo plugs are gapped smaller. That'd do it too.
mmmv,
M.
I haven't pulled a log recently but when I did I found next to no misfires. Plugs are correct for the vehicle and were replaced and properly gapped when the engine was rebuilt. IAM always stayed at 1. It might just be normal for this engine. I just have no "control" to be able to tell.
 
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