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Old 06-19-2018, 11:21 PM   #1
menard32
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Member#: 483378
Join Date: Mar 2018
Default 2002 WRX Studder Under Load

Firstly, I've read every thread on the main WRX sites about this issue and performed every fix I've found to no avail. Please, I need your guys' help. I have a 2002 WRX bone stock except for an aftermarket 3" downpipe with a possible exhaust leak (prev. owner put it on). The fixes I have found and tried are new spark plugs, new coil packs, cleaning MAF sensor, new fuel filter, using premium gas, new o2 sensor, and resetting the ECU after all of it. The power cut/studder happens almost exactly on 4,000 rpm. Another fact of note is that I believe I do have a small boost leak and my CEL is on, but it has always been on since I purchased the car. The only things I have found for possible results are: an old clogged fuel pump sock or a tune may be needed with the aftermarket 3" downpipe. However, the issue just started occurring less than a month ago, so I don't believe the downpipe is the issue unless it just sprung its leak and that shifted the car off tune? Please, I really need you guys' help on this. I'm drawing blanks.
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Old 06-20-2018, 11:06 AM   #2
PVNRT
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Member#: 483821
Join Date: Mar 2018
Vehicle:
2004 WRX 2.0 18g

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You really should pick up a tactrix and find out what the code is, then use it to make a log while driving. See what your long term fuel trims are. These cars have a huge potential for vacuum leaks especially at that age. I found 5 vacuum leaks on my used 04 and the guy was daily driving it this way.

Your ltft will help show if there is a vacuum leak as the ecu will always be trying to correct the mixture. I bet your turbo inlet is ripped, the oem ypipe will start to crack also at this age.

Its a good idea to chase all your underhood grounds too, the bolt end can loosen up and let in corrrosion.
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Old 06-20-2018, 12:43 PM   #3
Samurai Jack
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Member#: 21145
Join Date: Jul 2002
Chapter/Region: NESIC
Location: Not in my own time
Vehicle:
2002 Enemy of Aku

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Like PVNRT said:
- check for vacuum leaks on all your vacuum hoses
- check your OEM turbo inlet
- you make have cracks / bad gaskets between your UP / DP / connections to turbo

The OEM turbo inlet gets cracked and/or degraded at the turbo where it actually melts. It will need to be replaced.
- If this is true, you will have to pull the intake manifold to do the swap. May as well get a silicon turbo inlet AND check all your fuel lines at the same time.

As far as a tune, you do not need a tune for any of the mentioned items above since the 2002 ECU is more forgiving. If you get a tune, then you can optimize the changes and the motor tune so it would be a good thing.
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Old 01-17-2019, 02:55 PM   #4
s.ouzou
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Member#: 495114
Join Date: Dec 2018
Location: Reno
Vehicle:
2002 Subaru WRX
Blue

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Quote:
Originally Posted by menard32 View Post
Firstly, I've read every thread on the main WRX sites about this issue and performed every fix I've found to no avail. Please, I need your guys' help. I have a 2002 WRX bone stock except for an aftermarket 3" downpipe with a possible exhaust leak (prev. owner put it on). The fixes I have found and tried are new spark plugs, new coil packs, cleaning MAF sensor, new fuel filter, using premium gas, new o2 sensor, and resetting the ECU after all of it. The power cut/studder happens almost exactly on 4,000 rpm. Another fact of note is that I believe I do have a small boost leak and my CEL is on, but it has always been on since I purchased the car. The only things I have found for possible results are: an old clogged fuel pump sock or a tune may be needed with the aftermarket 3" downpipe. However, the issue just started occurring less than a month ago, so I don't believe the downpipe is the issue unless it just sprung its leak and that shifted the car off tune? Please, I really need you guys' help on this. I'm drawing blanks.
Make sure you gap the spark plugs to 0.025. I had the exact same problem and the gap solved the problem. Also, check the connections to your coil packs and make sure your coil packs are all working correctly.
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Old 01-17-2019, 11:06 PM   #5
AnonymousWrex
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Member#: 458426
Join Date: Nov 2016
Chapter/Region: TXIC
Location: Dallas
Vehicle:
2003 Impreza WRX
Black

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my 03 wagon just needed new grounds... but if you have a CEL make that go away first, then deal with your 4k rpm stutter, odds are theyre related
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