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Old 06-11-2017, 03:09 PM   #1
Scooby Newbie
Member#: 413694
Join Date: Feb 2015
Default 02 WRX mysterious issue

I have a 2002 WRX with 196k miles on it and am having a difficult issue to diagnose. The car has a cobb stage 2+ tune with a uppipe, downpipe, turbo inlet, boost controller and a intake. The car idles well and runs normal until 3500 rpms where it then starts to spit and sputter and misfire under boost. Car normally boosts to 15-17lbs and now will only go to 10ish lbs. I put a fuel pressure gauge on the car and it read about 45 psi at full throttle (low) and i replaced the factory pump with a walboro 255 and it didn't fix the problem. I have looked the car over for boost leaks several times with no luck. I swapped the Fuel pressure regulator with a spare with no change. Only codes the car would display is misfire codes occasionally when at WOT above 3500 rpms and it varied on cylinder each time. I have pulled plugs and checked gap, swapped plugs with other known good ones, swapped a coil with a known good coil, switched coil positions, all with no change. I take the car to a experienced Subaru and he ruled out fuel as a issue and diagnosed it as a bad MAF, i replace the MAF with a new one and the car gains a little improvement in power at WOT for a couple pulls and then goes back to the same issue. The only time i had luck with the issue going away is when i pull the fuel pressure regulator vacuum hose off the intake manifold and the car will boost to 10-12 lbs without a misfire or sputter. The issue will only happen occasionally with the FPR vacuum hose unplugged.
Any recommendations or past experiences that were similar are appreciated
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Old 06-12-2017, 01:58 PM   #2
Scooby Newbie
Member#: 456114
Join Date: Oct 2016
Chapter/Region: NESIC
Location: upstate NY
02 wrx


I'm going through the same problem. 02 wagon blouch16g, catless up, Tomei inlet, tgv deletes, 650 inj, DW45 fp. Just three days ago my car was boosting fine up to 20psi. Now I can barely touch the throttle without it sputtering and maybe misfires? I'm gonna do the plugs, I already ran all the fuel out, and checked for boost leaks and found none. No vacuum leaks either I'm stumped.
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Old 06-12-2017, 02:09 PM   #3
Scooby Specialist
Member#: 29292
Join Date: Nov 2002
Chapter/Region: SCIC
Location: Orange County CA
2004 WRX wagon


when my car was doing that, we tried to change alot of different stuff, found out when I changed all the coils and plugs it stopped
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Old 06-12-2017, 11:29 PM   #4
Scooby Newbie
Member#: 417685
Join Date: Apr 2015
Chapter/Region: Tri-State
Location: Pennsylvania
2003 Impreza WRX
Sonic Yellow


That does sound like an ignition issue. I'd check the plugs and coil packs. Is it throwing any codes?
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Old 06-13-2017, 09:32 AM   #5
Samurai Jack
Scooby Guru
Member#: 21145
Join Date: Jul 2002
Chapter/Region: NESIC
Location: Not in my own time
2002 Enemy of Aku


Did this just start after the COBB items were installed or has it been a while after the install?

Given the age & mileage, I'd suggest the same as subaru_gc8; change all plugs and coils. Coils only last so long.
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Old 06-15-2017, 12:16 PM   #6
Scooby Newbie
Member#: 455505
Join Date: Sep 2016
Chapter/Region: NESIC
Location: CT
2002 WRX


I had a similar issue in cylinder 3. Switched coil pack with cylinder 1 - that didnt fix it. Changed cylinder 3 injector connector - that wasnt it. Moved spark plug 3 to cylinder 1 and replaced the coil pack connector on cylinder 3. Fixed

Car had strange surging under load which eventually became a misfire under load. Finally ended up a steady misfire in 3.
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Old 06-15-2017, 03:18 PM   #7
Scooby Specialist
Member#: 333468
Join Date: Sep 2012
Chapter/Region: RMIC
Location: SLC, UT
1993 SS
03 WRB GD 205/22T 20G-XT


I had a similar issue. My battery terminal connection was loose and it would vibrate at higher rpms. Guess I got lucky mine was a simple fix.
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Old 06-20-2017, 02:16 PM   #8
Scooby Newbie
Member#: 247561
Join Date: May 2010
Chapter/Region: MWSOC
Location: Minneapolis, MN
2011 TR-42S


If you power cycle the engine does it go away for a while?
Mine does the same as what you describe, but if I am coasting, key off, key on, pop the clutch to start I can make boost for a while (few minutes) then it starts with the issue of no boost over 10 psi.
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Old 06-20-2017, 04:31 PM   #9
Scooby Newbie
Member#: 364356
Join Date: Aug 2013
Chapter/Region: HIIC
Location: Honolulu, Hawaii
2000 Forester (s)
Silver/black (two tone)

Default similar issue

I cleaned my IACV, MAF, CRANK, and CAM sensors and one of them fixed my misfire under boost. You should also check your timing, mine wasnt off but i heard 1 tooth can cause something similar to your issue.
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Old 06-21-2017, 02:29 PM   #10
Blue Meeko
Scooby Newbie
Member#: 344674
Join Date: Jan 2013
Chapter/Region: MAIC
Location: Abington,Pa
2003 Impreza wrx


Replace coil packs. ( with factory ones).
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