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Old 11-29-2022, 09:01 PM   #1
Apollo49
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Default 2004 WRX Hesitation

Hello, I've been having issues with my car lately and I cannot figure out what it is. Whenever I get to around 13 PSI on my turbo my car starts throwing a fit and there's a lot of popping going on and what not. Obviously it's misfiring, and it only does it when my turbo is in the 13-16 PSI range, (16 is the max its set at). I've changed the spark plugs, and for the first pull it was fine. After that it started doing it again.

I imagine my next move would be to change the MAF or Coil packs. I don't want to throw parts at it, so I'd like to learn what I can do in order to isolate the actual issue. Again, it only misfires at higher throttle.

I also thought that maybe it was a fuel issue? Maybe I should change my fuel filter? I replaced the old pump about a year ago. Should I buy a fuel pressure gauge and test it out?

190k miles
Cars stock.
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Old 11-30-2022, 07:51 PM   #2
subaru_gc8
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your coils are going bad
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Old 11-30-2022, 11:02 PM   #3
Apollo49
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Quote:
Originally Posted by subaru_gc8 View Post
your coils are going bad
OEM replacements or a better recommendation?
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Old 12-02-2022, 02:14 AM   #4
b_bercovitz
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OEM coils are pretty decent for most reasonable applications.
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Old 12-04-2022, 05:03 PM   #5
subaru_gc8
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oem don't need anything else, but make sure they're from subaru
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Old 12-06-2022, 04:24 PM   #6
Apollo49
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I figured you'd normally get a misfire code for this, is there any way i can tell for sure before i buy these?
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Old 12-06-2022, 05:56 PM   #7
Gixhost
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I had a similar issue some years ago. I wasn't sure what was happening at first. Once I figured out it only occurred on boost. I ended up taking it to my local shop and it was a coil pack...I know at some point the CEL came on as I was waiting to take it to the shop but initially it wasn't on.
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Old 12-06-2022, 06:08 PM   #8
Apollo49
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Quote:
Originally Posted by Gixhost View Post
I had a similar issue some years ago. I wasn't sure what was happening at first. Once I figured out it only occurred on boost. I ended up taking it to my local shop and it was a coil pack...I know at some point the CEL came on as I was waiting to take it to the shop but initially it wasn't on.
Thank you for the input, Iíll take your word on this and hope that this fixes things.
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Old 12-08-2022, 03:14 PM   #9
monkeyposeur
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I posted this a while back in this thread: https://forums.nasioc.com/forums/sho...5#post46735985

Quote:
Originally Posted by monkeyposeur View Post
Stuttering/hesitation/bucking can have so many causes and many of them can share the exact same symptoms which can be extremely frustrating as you have discovered.

I had a stalling/stuttering issue and it turned out it was the coilpack(s). NGK coil packs from RockAuto are great. They run about $62 each. I would advise against getting cheap ones.

Things I checked/replaced before the coil packs:
Checked ECU for stored codes
Reset ECU multiple times
Ran new ground lines
Checked fuel pump and fuel pump sock (there have been instances where the sock gets so clogged up it causes fueling issues)
Replaced fuel filter
Replaced fuel pressure regulator
Checked for boost leaks (found a loose intake coupler)
Replaced MAF with a new spare I had laying around
Replaced Spark Plugs.
Replaced alternator with new higher output voltage unit (had it laying around)
Logged during pulls - no knock detected.

I had no misfire codes which also made the problem hard to track down.

After I replaced all four coil packs the car was pulling like it used to. Replacing the coil packs was last on my list of things to do, so it was a frustrating process.

When I replaced the coils I wasn't even sure if it was going to help so I didn't bother and try to isolate which coil(s) were causing the problem. Do yourself a favor and just replace all four.
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Old 12-08-2022, 07:33 PM   #10
subaru_gc8
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FYI it takes a lot for the cel to come on for a misfire code on the 2002-2005 wrx, especially if it only occurs when on boost
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Old 12-10-2022, 09:12 AM   #11
Apollo49
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Just replaced them, took it for a drive and all was good. Thank you everyone for your help ***128077;
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Old 12-16-2022, 11:14 PM   #12
Unabomber
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Quote:
Originally Posted by Apollo49 View Post
Just replaced them, took it for a drive and all was good. Thank you everyone for your help
Good, now replace your boost control solenoid with a new Subaru one and your MAF with an OEM Denso from amazon. Do both today. https://forums.nasioc.com/forums/sho....php?t=2740715
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Old 01-05-2023, 04:25 AM   #13
Jengacat
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I actually had similar issues that plagued my '02 for a while when I first got it; ended up being fuel filter. You already fixed yours, but if you haven't replaced the in-bay fuel filter for the time you've owned the car might be time
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Old 01-29-2023, 08:05 PM   #14
SpooksWRX
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following
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