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Discussion Starter · #1 ·
Hi guys looking for some help diagnosing a cylinder 1 misfire on my 2004 wrx.

Mods
K/n Typhoon intake
Invidia up + downpipe(catted)
DW fuel pump
sti pinks
cobb 3 port ebcs
perrin turbo inlet
grimspeed aos
protuned with cob AP v3
Problem
Cylinder 1 will occasionally misfire when engaging the clutch(Car goes under load). Typically happens after taking off from a stoplight but can also occur when shifting up or down.
Sluggish at low rpm(<2000).
CEL is present. Cylinder 1 CEL + rarely a Cat insufficiency CEL
Idle is somewhat rough. I can hear it fluctuate between two different tones. NO CEL or misfires at idle.
Info from Cobb AP
DAM is consistent 16
AFR is ~14 at idle
Air Fuel Correction is ~negative 10. AF learning A1 ~negative 14. Car is pulling lots of fuel at idle?
I hit target boost(17.5psi)
Attempted Solutions
New spark plug(NGK Iridium)
New coil(OEM)
New fuel injector(OEM sti pink)
Compression tested cylinder 1: 155psi
Possible Solutions?
Clean IACV. Waiting on a gasket to do this.
Replace front 02 sensor. Part is expensive so I don't want to just replace it without knowing if it's the problem.
 

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Could be a boost leak issue, misfiring will be common at sub 2k RPM and under load. It's really not ideal to be giving it much throttle in that situation especially in 3rd 4th and 5th.

Is this ongoing or recent? On occasion I'll get a bad batch of fuel that will cause some oddness but usually it will show as my dam will drop temporarily.

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Discussion Starter · #3 ·
Hey XJman thanks for the response.

I doubt it's a boost leak as I consistently hit my target boost. I also ran a smoke test a couple months back and found no leaks.

This is an ongoing problem as the misfires are not always present. I can often commute to work and see no misfires for the full 20 miles, only to see them on the way back from work.
The car has been through multiple tanks of gas, and my DAM never drops below 16.

However I've noticed that the Accesport will record high feedback knock values(4~8) when the car shifts(at higher gears), but I've always assumed they are false cases as my DAM is always 16.
 

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Because of the idle thing i still lead to something prior to the O2 sensor although it can cause similar issues. Wandering idle, weak idle, a car that suddenly dies when coming off throttle would lead me towards a vacuum leak.

Do you have issues when your getting on it or is it mostly low speed cruising?

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Discussion Starter · #5 ·
The car stumbles when the clutch engages, usually causing a misfire. Once I'm in gear it's fine until I shift.
Mostly Low speed cruising. Never have a problem cruising at highway speeds, or WOT pulls
 

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Just trying to catch simpler things. have you checked the pre turbo intake for a leak?

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Discussion Starter · #7 ·
I'd done a smoke test a couple of months back and found nothing pre-turbo. Haven't changed any parts since then. My car is pulling fuel at idle so I assumed there isn't any extra air getting in there.
 

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You can find a "economy" front O2 sensor for around $60 on ebay, made in Japan too.
If it solves your problem, it's temporary until you get yourself a quality replacement.
Just had the problem on my Stage 2 bugeye.
 

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I'd done a smoke test a couple of months back and found nothing pre-turbo. Haven't changed any parts since then. My car is pulling fuel at idle so I assumed there isn't any extra air getting in there.
The only thing left that I doubt is the problem is the MAF sensor. If you are getting good fuel, air flow is correct, and you've got good compression. Knock sensors can sometimes fail as well or register false knock.
You can find a "economy" front O2 sensor for around $60 on ebay, made in Japan too.
If it solves your problem, it's temporary until you get yourself a quality replacement.
Just had the problem on my Stage 2 bugeye.
Don't waste your time, I went through thinking my 2011. Buy the correct denso sensor from rockauto, or the factory unit from subaru

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Discussion Starter · #11 ·
MAF Sensor was cleaned when i did the smoke test.

I've read the misfire thread and I've tried 90% of the stuff on it. The ones I haven't involve buying parts/tools I rather not buy if not necessary.
 

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Pallino said:
MAF Sensor was cleaned when i did the smoke test.

I've read the misfire thread and I've tried 90% of the stuff on it. The ones I haven't involve buying parts/tools I rather not buy if not necessary.
What exactly have you done? Because the list in your OP and subsequent posts doesn't add up to 90%...
 

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Discussion Starter · #13 ·
Sorry If it isnt exactly 90% I was generalizing and meant I've done the majority of what I believe is relevant to my case. Please correct me if I'm wrong. Thanks.
From the misfire thread this is what I've done...
1. Wrong, worn or incorrectly gapped spark plugs.
Replaced spark plug
2. Clogged/dirty/bad injectors or fuel filter
Replaced injector. Replaced my fuel filter 3 months back when I first did sti pink swap.
3. Check valve clearances & compression
Checked misfiring cylinder compression 155 psi. Heads were redone less then 15k miles ago so I'm assuming the valve clearance is in spec.
4. Dirty MAF sensor
Cleaned it
5. Vacuum leaks or preturbo leak
Smoke test done no leaks. Perrin inlet has less then 5k on it.
6.Poor grounds/grounding
Inspected grounds they seem OK.
7. Cam timing.
Haven't checked. Timing doesn't seem to be the issue due to my case.
8. Excessive PCV blow by
DAM is always 16. I have an AOS
9. Carbon build up in heads/cylinders.
Haven't checked. I doubt this is the issue due to low miles on pistons + head rework.
10. Lightweight flywheels or crank pulleys
Flywheel + pulleys are all stock.
11. Bad/loose coil pack or coil pack connector
Replaced coil. Connector looks good.
12. Faulty fuel pressure regulator or fuel pump
Fuel pump was done 3 months back along with the sock. Haven't tested fuel pressure but the car runs great at wot and my AFR seems ok.
13. Faulty front O2 sensor
Considering trying this if cleaning the IACV doesn't help. No CEL for it makes me doubt it is bad though.
14. Damaged crank timing gear
Haven't checked but I doubt timing is my problem.
15. Misfires all cylinders
Mine is only cylinder 1
 

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This topic is a number of months old but I wanted to throw out a solution that for the same symptoms I had with my 2004 WRX. I had very rough idle (around 500 rpm and on the verge of apparent stalling) and was throwing code P0457 "Evaporative Emission Control System Leak Detected(gross leak)." Checked the simple stuff like gas cap, fuel filter connections, etc and reset code. Then... it it still was running rough and threw the cylinder 1 misfire code the OP references. Well, searching elsewhere online it turns out that cylinder 1 has a connection to the Evaporative Purge Valve (partially disconnected in picture). Took that off, cleaned it (blew it out lightly), and reinstalled. Turned it over and issue immediately remedied. Purring like a kitten still...
 

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