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Old 03-05-2014, 08:42 AM   #1
Sid03SVT
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Join Date: Jun 2008
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2006 WRX Wagon
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Question 06 wrx MT, stock, high rpm issues 3rd & 4th

Alright Suba-gurus I need your help.
The car is a 2006 WRX wagon with MT, bone stock, just ticked over 77k miles.

Car is a DD and well maintained, Subaru parts & fluids per the manual schedule, Rotella T6 at 3,750mi or 4 months (whichever comes first).
No fluid leaks, not using/burning any oil or coolant; more or less an issue free family wagon.

At about 5,500-5,750 RPM in 3rd & 4th gear at WOT I am experiencing an immediate loss of power - it feels similar to hitting the rev limiter.

This does not happen when revving freely, or in 1st or 2nd; I'm unsure about 5th because I'd have to be going pretty darn fast to test that, and I just don't go that fast in cages on public roads anymore.

No dash lights.

My initial thought is the fuel filter as I have not done it yet; but I'm hoping maybe someone out there in the community has experienced this and has some idea what it is.

Thanks in advance <aTdHvAaNnKcSe>
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Old 03-05-2014, 10:37 AM   #2
Brother EddieJ.
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6speed/ 330whp/ 300wtq

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Why is your first thought fuel filter? Your first thought should be vac leak. Do not do any "testing" in 5th, too much load on the motor.

We need to know current mods please. And if you have a boost gauge what is the idle vacuum? Are you hitting full boost as well?

And just so we are clear when you experience this loss of power the car; bucks, shudders and falls on it's face? It's a violent loss of power or do the RPMs just jump with no power? Then picks back up like nothing happened?
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Old 03-05-2014, 11:35 AM   #3
Sid03SVT
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Join Date: Jun 2008
Location: CT
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2006 WRX Wagon
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Quote:
Originally Posted by Brother EddieJ. View Post
Why is your first thought fuel filter? Your first thought should be vac leak. Do not do any "testing" in 5th, too much load on the motor.

We need to know current mods please. And if you have a boost gauge what is the idle vacuum? Are you hitting full boost as well?

And just so we are clear when you experience this loss of power the car; bucks, shudders and falls on it's face? It's a violent loss of power or do the RPMs just jump with no power? Then picks back up like nothing happened?
my first thought was fuel filter for a few reasons:
1.) it's the only maintenance item that hasn't been performed
2.) the issue only manifests in 3rd and 4th under WOT at approx. 5500-5750 rpm - and it feels similar to hitting the rev limiter ie. fuel cut-off, and if the filter is restricted I'd assume an issue would manifest during extended high fuel demands (ie. upper gears, higher RPM).

why I didn't go to vac leak first:
1.) idle RPM is solid
2.) throttle response is not sluggish
3.) when I release the gas pedal (out of gear), the RPM drop to idle RPM, they don't dive below idle and recover.

Mods: NONE, bone stock as mentioned in the original post

it does have a boost gauge in megapascal (MPa)
Idle Vacuum: will check this afternoon
Hitting Full Boost: yes, but will confirm again this afternoon; approx. 0.075MPa (10.8-11 psi) which from what I read is where a stock WRX peaks.

As far as loss of power - it feels like hitting the rev limiter, so do not pass go, do not collect 200 dollars. Instantaneous halt to acceleration at approx. 5,500-5,750 RPM; as if someone cut off the fuel.

I have gone through the rev range to redline in 3rd at partial throttle and it's fine, only at WOT in 3rd or 4th is it an issue.

appreciate the input, and look forward to replies.
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Old 03-05-2014, 11:44 AM   #4
Brother EddieJ.
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I had the same issue. Felt like I hit a brick wall from 1-10psi and 4-6k RPMs. My afr pegged at 10:1 then would pull itself to 11.2:1 Not sure if I was hitting full boost didn't push it. My vac was fine at idle. Car was good as long as I stayed out of boost. I thought my FPR vac line had a hole in it. It was a basic vacuum leak in my charge pipe or my BPV. No idea really, I just tightened everything and reset my ecu. I went through every vacuum line and spent hours checking and re-checking everything that could cause the symptoms. Finally I fixed it, but not sure what exactly it was, but it was a vacuum leak.
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Old 03-05-2014, 01:36 PM   #5
dstroy
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If you think it's the fuel filter, why haven't you changed it yet?
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Old 03-05-2014, 02:02 PM   #6
Sid03SVT
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Quote:
Originally Posted by dstroy View Post
If you think it's the fuel filter, why haven't you changed it yet?
A few reasons actually.

1.) I hardly ever get into that RPM range in 3rd or 4th gear, maybe once every three months, so it's not an issue that affects me regularly. Outside of that particular RPM, gear and WOT combination, I do not see this issue.
2.) it's winter in New England and I don't have a heated garage to work in (unheated garage though).
3.) it's an in tank fuel filter and requires removal of my rear seat and hatch area interior pieces to get at (aka I'm a little lazy).

My plan was to do the fuel filter in the spring when it's warmer out regardless of this issue, but I'm not certain that the fuel filter is the culprit, so I want to probe the internet/NASIOC for other possible causes. Checking for vacuum leaks is less invasive than dismantling my interior and swapping the fuel filter, so I'll give that a whirl this weekend.

I'm still looking for other possible reasons however, so if anyone has experienced a similar issue please chime in.
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Old 03-05-2014, 02:09 PM   #7
Torontolegacy
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Vacuum leaks can behave oddly. Im leaning towards a leak aswell. Just because idle and response is ok doesnt mean you dont have a line or fitting open up under boost/high load.
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Old 03-05-2014, 03:03 PM   #8
dstroy
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Location: Newport
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2012 STI sedan
Black with scratches

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Quote:
Originally Posted by Sid03SVT View Post
A few reasons actually.

1.) I hardly ever get into that RPM range in 3rd or 4th gear, maybe once every three months, so it's not an issue that affects me regularly. Outside of that particular RPM, gear and WOT combination, I do not see this issue.
2.) it's winter in New England and I don't have a heated garage to work in (unheated garage though).
3.) it's an in tank fuel filter and requires removal of my rear seat and hatch area interior pieces to get at (aka I'm a little lazy).

My plan was to do the fuel filter in the spring when it's warmer out regardless of this issue, but I'm not certain that the fuel filter is the culprit, so I want to probe the internet/NASIOC for other possible causes. Checking for vacuum leaks is less invasive than dismantling my interior and swapping the fuel filter, so I'll give that a whirl this weekend.

I'm still looking for other possible reasons however, so if anyone has experienced a similar issue please chime in.
I feel you man, I'm stationed in Newport right now. At least I have the hobby shop on base to go to. It doesn't take that long to get the seat out and pull the basket, >30mins but it has been wicked cold.
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Old 03-05-2014, 04:32 PM   #9
Sid03SVT
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Member#: 183032
Join Date: Jun 2008
Location: CT
Vehicle:
2006 WRX Wagon
Silver

Default

Quote:
Originally Posted by Sid03SVT View Post
my first thought was fuel filter for a few reasons:
1.) it's the only maintenance item that hasn't been performed
2.) the issue only manifests in 3rd and 4th under WOT at approx. 5500-5750 rpm - and it feels similar to hitting the rev limiter ie. fuel cut-off, and if the filter is restricted I'd assume an issue would manifest during extended high fuel demands (ie. upper gears, higher RPM).

why I didn't go to vac leak first:
1.) idle RPM is solid
2.) throttle response is not sluggish
3.) when I release the gas pedal (out of gear), the RPM drop to idle RPM, they don't dive below idle and recover.

Mods: NONE, bone stock as mentioned in the original post

it does have a boost gauge in megapascal (MPa)
Idle Vacuum: will check this afternoon checked and its -0.078 MPa or -22.6 inHg if my math is correct (when warmed up A.C. off)
Hitting Full Boost: yes, but will confirm again this afternoon; approx. 0.075MPa (10.8-11 psi) which from what I read is where a stock WRX peaks. Verified, might be a tick over 0.075, but no more than 0.077, noticed boost starts to taper off at higher RPM while under WOT down to 0.072

As far as loss of power - it feels like hitting the rev limiter, so do not pass go, do not collect 200 dollars. Instantaneous halt to acceleration at approx. 5,500-5,750 RPM; as if someone cut off the fuel.

I have gone through the rev range to redline in 3rd at partial throttle and it's fine, only at WOT in 3rd or 4th is it an issue.

appreciate the input, and look forward to replies.
So this is where I'm at, will be checking for vacuum leaks this weekend, and swapping out the fuel filter in the spring regardless of whether or not I have a vacuum leak.
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Old 03-08-2014, 09:22 PM   #10
123mfg
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You might consider bypassing the factory fuel filter with some Gates 27093 submersible hose. I just did the fuel filter in Jan. and the O-ring on it blew out about two weeks ago leaving me stranded. It was a Subaru OEM filter. I did have a Walbro 255 behind it but the design of the filter is less than robust for high pressure applications. I am going to put an aeromotive filter under the hood for easier maintenance and better reliability.

--just my .02
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