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Old 04-16-2021, 09:22 PM   #1
Caldor
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Member#: 523754
Join Date: Apr 2021
Vehicle:
2004 STI

Subaru Banner 2006 WRX boost hesitation and shutters.

Hey everyone, new member here. I have had some Subaru's for about 10 years and used them for my job but never had any WRX's or turbo engine ones. Been told to stay away pretty much from a local mechanic. My son really wanted one so I ended up buying a pair of them an 04 WRXSTI and a 06 WRX.

So here I am with questions on some issues. It has a lot of upgrades on the car. Was going to post a picture with a list but couldn't figure it out at this moment. So here goes.

The car seems to run but one you get some boost it is like it stutters, maybe backfires and then goes more. Seems like the boost gets up to about 10 on the Cobb then drops to almost 0 then jumps back up. Makes the car stutter and jerk. Throws some misfire codes also. I am not familiar with all the workings in the car as the turbo stuff is all new to me. Looks like it was tuned by JM Automotive in Minnesota according to the Cobb map running 91 fuel and 19 PSI. Sounds maybe like a vacuum leak but maybe not since I am new. I have a Cobb log also. Here is a quick list of what the car should have.
EJ257 Block
Ej255 heads
VFF48 Turbo
38mm Tail EWG with Grmspeed up Pipe
Turbo XS Fmic
Uel Headers
Invidia Downpipe
Grimspeed 3 port EBC
SPT Intake
Perrin Turbo inlet
Grimspeed internal Wastegate bracket
Perrin Pitch stop
Perrin Lightweight crank crank pulley
Mishimoto Radiator and fan shround
Mishimoto Exp tank and thermostat
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Last edited by Caldor; 04-16-2021 at 09:38 PM.
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Old 04-17-2021, 06:57 AM   #2
Jay11STI
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Member#: 492422
Join Date: Oct 2018
Chapter/Region: Tri-State
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2011 STI

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Well first things first, have you checked for any vacuum and or air leaks? Also when what the the last time spark plugs were changed?
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Old 04-17-2021, 02:11 PM   #3
Caldor
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Quote:
Originally Posted by Jay11STI View Post
Well first things first, have you checked for any vacuum and or air leaks? Also when what the the last time spark plugs were changed?
Not yet, from reading some posts that is what I plan to do. Any specific places to check? Figured I would follow the airflow and see if I see anything . Like I said it is all new to me but we will see how it goes. Spark plugs are unknown also.
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Old 04-17-2021, 02:17 PM   #4
K3rm1tth3fr0g
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Member#: 508105
Join Date: Nov 2019
Chapter/Region: NWIC
Location: Greater Seattle Area
Vehicle:
Link G4X flex tuned
02' EJ205 20G 6MT wagon

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Quote:
Originally Posted by Caldor View Post
Not yet, from reading some posts that is what I plan to do. Any specific places to check? Figured I would follow the airflow and see if I see anything . Like I said it is all new to me but we will see how it goes. Spark plugs are unknown also.
Test for boost leaks in the intake specifically. There are ways to do it with smoke or with soapy water. YouTube and Google will show you how.

You can have a shop do it or make a boost leak tester.

Also clean (or preferably replace) your maf.
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Old 04-17-2021, 03:13 PM   #5
Jay11STI
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Location: North Jersey
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2011 STI

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Quote:
Originally Posted by Caldor View Post
Not yet, from reading some posts that is what I plan to do. Any specific places to check? Figured I would follow the airflow and see if I see anything . Like I said it is all new to me but we will see how it goes. Spark plugs are unknown also.
Do a boost leak test, you will be surprised to see what actually leaks. There are a bunch of ways to do a boost leak test and you can even build your own if your crafty. Or you could just buy your own tester. Either way, highly recommend starting off with that and doing spark plugs.
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Old 04-21-2021, 06:05 AM   #6
MasterOfNone_
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Location: Palmdale, CA
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2012 WRX
Black

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Post some logs if you can
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Old 04-21-2021, 08:49 PM   #7
Caldor
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2004 STI

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Quote:
Originally Posted by MasterOfNone_ View Post
Post some logs if you can
Let me know if this works. Wasn't sure how you can show the log.

https://1drv.ms/x/s!AmnHR3a0tEDq4k4W...-h_YI?e=QGgdob
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Old 04-21-2021, 09:40 PM   #8
ASP_SyNdicate
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with a car that age, try replacing your MAF sensor if you never had. every calculation the engine makes is based on that. worked wonders on my 05 LGT. better idle was especially noticeable.
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Old 04-21-2021, 11:07 PM   #9
Caldor
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The previous owner replaced it within the last 6 months. I am going to double check to make sure it was the correct part number and I also bought some MAF cleaner just in case.
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Old 04-22-2021, 03:27 AM   #10
MasterOfNone_
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Quote:
Originally Posted by Caldor View Post
Let me know if this works. Wasn't sure how you can show the log.

https://1drv.ms/x/s!AmnHR3a0tEDq4k4W...-h_YI?e=QGgdob
there was some pretty high and consistent knock for a short period of that log.
can you post another log but also log AFR, AF correction 1, Inj Duty Cycle and only log a 1-2min cruise log and then log where the issue happens.


but based on your symptoms. check for boost leaks, check your coil packs, spark plugs and spark plug gap. also get the car to operating temp then take off the oil cap and check for any smoke coming out. if theres any smoke coming out then good bye engine. do a compression and leakdown test. good luck
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Old 04-22-2021, 11:58 AM   #11
Caldor
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2004 STI

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Quote:
Originally Posted by MasterOfNone_ View Post
there was some pretty high and consistent knock for a short period of that log.
can you post another log but also log AFR, AF correction 1, Inj Duty Cycle and only log a 1-2min cruise log and then log where the issue happens.


but based on your symptoms. check for boost leaks, check your coil packs, spark plugs and spark plug gap. also get the car to operating temp then take off the oil cap and check for any smoke coming out. if theres any smoke coming out then good bye engine. do a compression and leakdown test. good luck
Ok here is a few logs from this morning.

1st log was car up to temp and driving 50-65mph in 5th gear
2nd log was driving in 4th gear with higher RPMS same speeds
3rd log I go on it a decent amount but it bucked pretty hard
4th log was again the same, might of got on it a little more but it was decent no bucking, might of had a bit of skip
5th log was just normal driving from a stop sign up to about 50mph.

Seems like the knock on the COBB showed up more the slower I was going. Showed up a little more after the 5th log and higher numbers -6 or 8. It was lower RPMS and under 40 mph, was a few seconds.

https://1drv.ms/u/s!AmnHR3a0tEDq4lE1...7tZVq?e=WqR19y
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Old 04-22-2021, 12:12 PM   #12
Caldor
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Now that I am looking at some of the logs, looks like some of the info is missing maybe that you wanted. EDIT - My bad I didn't realize I needed to go into setup to select other stuff to log. Also wondering what items to most people activate in the log?

Last edited by Caldor; 04-22-2021 at 12:23 PM.
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Old 04-22-2021, 12:30 PM   #13
Jedi03
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2009 STi Blue
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to answer earlier question, most of the stuff that needs to be looked at is on top of the engine, some under the intake manifold, but with the front mount should be easy to access...would recommend compression test while you have plugs out, get used oil analysis to see motors health
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Old 04-22-2021, 01:03 PM   #14
Caldor
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2004 STI

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Originally Posted by MasterOfNone_ View Post
there was some pretty high and consistent knock for a short period of that log.
can you post another log but also log AFR, AF correction 1, Inj Duty Cycle and only log a 1-2min cruise log and then log where the issue happens.


Ok I added those items on the datalog. Car ran decent. Seems to always have a little hesitation once boost kicks in. No crazy jerking this time around. Datalogs 25-29 should be with the correct items you wanted to map. I cleared codes before all these logs today and there is no misfire code yet after both sets of log runs. Seems to take a little bit of time to pop back up.
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Old 04-22-2021, 06:35 PM   #15
Lessk-STI
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I actually came here because I'm having a similar issue.

For me it started out when I was leaving work one day. Got on it getting onto the highway and about 6K RPM I felt the power cut a bit and then shifting into 3rd the exhaust popping and a stutter feeling. It drives completely normal under 4K RPM and shifting easy. But if I put it under a load the stutter and popping exhaust comes back. When I was trying to figure out what was going on, I did get the orange check engine to flask 5 or 6 times and then go away. No codes have popped up either.

I replaced the MAF with a brand new one and it didn't change anything.

Last edited by Lessk-STI; 04-22-2021 at 06:49 PM.
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Old 04-22-2021, 08:09 PM   #16
Diavolo_
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Quote:
Originally Posted by Lessk-STI View Post
I actually came here because I'm having a similar issue.

For me it started out when I was leaving work one day. Got on it getting onto the highway and about 6K RPM I felt the power cut a bit and then shifting into 3rd the exhaust popping and a stutter feeling. It drives completely normal under 4K RPM and shifting easy. But if I put it under a load the stutter and popping exhaust comes back. When I was trying to figure out what was going on, I did get the orange check engine to flask 5 or 6 times and then go away. No codes have popped up either.

I replaced the MAF with a brand new one and it didn't change anything.
better if you start your own thread instead of hijacking someone elses.
when you do that, include the information about what car you have and the mileage.
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