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Old 11-06-2012, 05:22 PM   #1
simpsonsdotcom
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Member#: 269543
Join Date: Jan 2011
Location: Richmond, VA
Vehicle:
2002 2.5RS BRP
2004 WRX WRB

Default 2004 WRX Stutters and Pops under WOT

First Car info:
-Deadbolt TD-05 7cm 18g turbo (Ported and Polished/Ceramic Coated)
-TurboXS Front Mount Intercooler
-P&L Big MAF Intake
-Deatschwerks 740cc Injectors
-Walboro 255lph fuel pump
-Perrin Electronic Boost Control Solenoid (EBCS)
-Helix Downpipe (Hi-Flow Cat)
-Surewin V2 Catback Exhaust
-STi Bypass Valve (Crushed to hold more boost)
-STi Exhaust Manifold (Headers) (Ported and Polished/Ceramic Coated)
-Samco Turbo Inlet
-Mishimoto Radiator
-Mishimoto Radiator Hoses
-IAG V-Band External Wastegate Uppipe
-Tial 38mm External Wastegate

Car runs great under normal driving conditions, but under WOT it runs terrible (see youtube videos below)

3/4 throttle low boost normal smooth rev

WOT in 3rd gear Popping and Stuttering not hitting Target boost of 21

WOT in 6th gear Overactive bypass valve

Car idles at 26inHg
have changed spark plugs in the past week, changed oil (needed to be changed anyways), and did injector cleaner.
did a compression test over the summer all cylinders were about 160PSI

Last edited by simpsonsdotcom; 11-11-2012 at 09:05 PM.
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Old 11-07-2012, 09:05 AM   #2
czum09
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Location: Cedar Rapids, IA
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2002 WRX
WRB

Default

Vac leak, pre turbo, also check your EBC.
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Old 11-07-2012, 04:39 PM   #3
simpsonsdotcom
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Join Date: Jan 2011
Location: Richmond, VA
Vehicle:
2002 2.5RS BRP
2004 WRX WRB

Default

Thanks for your reply!

Wouldn't my idle vacuum be less than 26inHg?

I was thinking a possible cause being the EBC but how do I check it?
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Old 11-07-2012, 04:50 PM   #4
czum09
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Is your car tuned for the EBC? to check it you can hook it to a 12v power source and it should click.
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Old 11-07-2012, 04:57 PM   #5
simpsonsdotcom
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Default

yeah its protuned for everything on it.
So I should unplug it and just like run wires from the battery and probe the plug for the EBC?
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Old 11-07-2012, 05:52 PM   #6
czum09
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yeah, or get a known working ebc. I still tend to lean towards vac leak!
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Old 11-07-2012, 08:06 PM   #7
simpsonsdotcom
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Alright tested EBC its clicking.
I have looked though the vacuum lines and haven't seen anything out of place. Any suggestions where to look? I could have a vacuum leak and still register 26inHg?
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Old 11-09-2012, 12:50 PM   #8
simpsonsdotcom
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2004 WRX WRB

Default

Anyone have any tips for finding a vacuum leak or where to look first?

I have heard they you can spray carb cleaner on the vacuum hoses while the engine is running and listen for a change in idle. But if the leak is on a line going from the EBC to the wastegate it wouldnt change the idle would it?

Or if I can even have one with a boost gauge registering 26inHg during idle?
Thanks!
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Old 11-09-2012, 01:44 PM   #9
04reddragon
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what bov are u running??
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Old 11-09-2012, 01:55 PM   #10
simpsonsdotcom
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2004 WRX WRB

Default

Doesnt have a BOV
It has a STi Bypass Valve
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Old 11-09-2012, 01:59 PM   #11
04reddragon
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yea my bad just saw that, try crushing it a bit more and see if that makes a different my buddy had a simlair issue like this and had the bpv crushed a bit and crushed it more and the issue went away and holding boost a lot better
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Old 11-09-2012, 02:03 PM   #12
simpsonsdotcom
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2004 WRX WRB

Default

Thanks for the reply.
Was his working before and then stopped working though?
My car was fine about 2 weeks ago, and then over the course of about 2 days I noticed it acting up and has been ever since.
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Old 11-09-2012, 02:38 PM   #13
04reddragon
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yea his was an 05 wrx no biggie there and for a month ran smooth then one weekend he had me drive it and started notice on half throttle that his gauage was bouncing already and sputtering alot on wot no leaks and at the vac lines were ok but had to sway one out but it would still do it intill he smashed his bpv down a little more and went away after he took off the negative on the battery so the ecu can re learn and been running strong since
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Old 11-09-2012, 02:56 PM   #14
simpsonsdotcom
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2004 WRX WRB

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hmm. Yeah maybe Ill try that then. Do you have link to a write-up on how to do it?
Would it be worth it to just buy a Tial recirculating BOV?
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Old 11-09-2012, 03:02 PM   #15
04reddragon
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u can but i would try the steps above checking for vac leaks and making sure all lines to the turbo and turbo inlet are nice and tight cause in pressure this can happen. I would do that before spending any money or just replace it with another bpv thats another option i would consider.
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Old 11-09-2012, 03:16 PM   #16
simpsonsdotcom
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Default

K I agree, but just dont know where to start..

(from my earlier post)
Anyone have any tips for finding a vacuum leak or where to look first?

I have heard they you can spray carb cleaner on the vacuum hoses while the engine is running and listen for a change in idle. But if the leak is on a line going from the EBC to the wastegate it wouldnt change the idle would it?

Or if I can even have one with a boost gauge registering 26inHg during idle?
Thanks!
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Old 11-09-2012, 03:25 PM   #17
04reddragon
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try searching im sure theres a few threads showing how to do them.
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Old 11-10-2012, 06:06 PM   #18
simpsonsdotcom
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2004 WRX WRB

Default

So I still haven't found a vacuum leak.
I took the Bypass valve off and took it apart seems to be working properly. Spring tension is really tight. Do I just cave the end cap in a little further to crush it a little bit more?
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Old 11-10-2012, 07:17 PM   #19
UK-Wagon
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Its not a vacuum leak. Replace the Primary O2 sensor (before turbo). Had this happen to me before and seen it on customer cars plenty of times. Until you replace it, you need to stop driving it hard! You will blow it up soon if you continue to do so.

Go to Napa auto and get a Bosch replacement for about $135 or they also offer OE Denso sensors for $90
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Old 11-10-2012, 10:36 PM   #20
simpsonsdotcom
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2004 WRX WRB

Default

Ok this makes since.
I don't have a CEL, but i decided to have the AP check for codes anyways. It had P0037 HO2S heater control circuit low (bank 1 sensor 2) code. I didn't think much of it before because I found somewhere that many times tuners will turn off certain CELs because they will always be on. The car is new to me so I thought maybe it was just always throwing the code and I never knew.
Thank you!
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Old 11-11-2012, 11:10 AM   #21
oOIIJoshIIOo
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1 of three things...O2 sensor, coil pack(s), or maybe even oil leaking around spark plug hole. I had the same issue a while back and ended up being a coil pack but I didn't have an codes.
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Old 11-11-2012, 11:17 AM   #22
easterbran
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OBP

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I had the exact same stuttering/ popping issues on my 05 Sti, until I replaced the stock fuel pump with a Walboro 255. I'm willing to bet this is your problem. How many miles are on your car? My fuel pump went bad at 156,000 miles
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Old 11-11-2012, 11:19 AM   #23
novacivic
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Have you replaced your fuel filter?
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Old 11-11-2012, 12:36 PM   #24
simpsonsdotcom
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Join Date: Jan 2011
Location: Richmond, VA
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2004 WRX WRB

Default

I changed the plugs, and they actually looked really good, didn't need to be changed, but I figured I had new ones so I put them in. No oil or anything on the threads or tip so I doubt that is it. I was thinking coil packs too, but they are so expensive just to get one and they weren't in stock anyplace I decided to explore other roots first.

161,xxx miles. Fuel pump/filter could be the issue. Where is the filter on these?
If it was the pump wouldn't it just not work? Do they slowly go bad?

Thanks for the replies
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Old 11-11-2012, 01:27 PM   #25
easterbran
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Quote:
Originally Posted by simpsonsdotcom
I changed the plugs, and they actually looked really good, didn't need to be changed, but I figured I had new ones so I put them in. No oil or anything on the threads or tip so I doubt that is it. I was thinking coil packs too, but they are so expensive just to get one and they weren't in stock anyplace I decided to explore other roots first.

161,xxx miles. Fuel pump/filter could be the issue. Where is the filter on these?
If it was the pump wouldn't it just not work? Do they slowly go bad?

Thanks for the replies
Sounds like my exact thought progress (and my tuner's) when resolving my issue. My fuel pump went bad over the course of about a thousand miles. First, it began sputtering and hesitating only at WOT every once in a while. A hundred miles later, sputtered every time at WOT. stayed like that for 500 miles, then one day it was horrible. If I was in boost AT ALL, it would sputter. The last hundred miles before I changed the pump, the car was not driveable. It could barely get to 3k rpms, had like a 20 second 0-60, and felt like I was constantly engine braking. This had occurred after replacing the spark plugs, compression test, coil pack testing, and smoke testing (and fixing small Vac leak). The car wouldn't even start the day I was replacing the fuel pump. After the install, she ran beautifully again (after I replaced my front O2 sensor because of a poor idle and constant stalling)
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