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08 OBXT 5MT
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Discussion Starter · #1 ·
Hello!

So I've been getting an intermittent P0301 cylinder 1 misfire.

First thing I tried was replacing the coil packs which I did this past Thursday, but I decided not to look at the plugs at that time though I probably should have. I didn't want to risk unintentionally messing up the gap while taking them out or putting them back in.

I've been searching through posts about this and some are quite scary! Head and valve gasket leaks, burnt valves, busted ringlands, full engine wiring harness replacement, etc.

NGK One Step Colder plugs have 1.5 years and 20k miles on them (visually unchecked).

Pistons are forged so I doubt ringlands. Heads / valves are stock. It idles a little wonky sometimes, but the other 99% it runs fine and pulls strong.

A ground issue was mentioned but I'm not quite sure where to search for all grounds on my year. I see a couple under the car that look like they are connected but there may be others that I don't know of.

A compression test was mentioned to but I don't have the tools for this, nor have I done this before.

I also do not have a boroscope to have a look at the inside of cyl 1.

Any suggestions you all may have would be appreciated. I have a fairly lengthy road trip coming up in 2 weeks so I'm hoping this isn't anything serious.
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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you might be able to borrow a boroscope,
off a parts store. (these things are really typical now, pro mechanics may have more then one).
 

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Master Caster
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Why the colder plugs?

You have to check the plug and gap.

Also check the coil plug quick connect. They are famous for fatiguing and not fully clicking in place or breaking off. You can actually zip tie them on (to keep pressure) if you can't get a replacement end. They are not hard to change. But you need a salvage harness or the proper new connector.

I have had misfiring issues from this before.

Do you have any drive-abilty issues? Idles wonky sometimes? Intake/Vacuum leaks?

Have you checked fuel pressure?
 

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2005 Legacy GT wagon 5MT Limited
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The procedure for diagnosing a single-cylinder misfire is as follows:
1. Swap the #1 & #3 ignition coils and see if the misfire follows. If so, replace the bad coil. If not,
1.5. On Subarus, the coil connector pins can get a little loose. Give them a tiny twist with needle-nose pliers to ensure the connection is snug. Assuming that doesn't do it,
2. Swap spark plugs. If those check out,
3. Swap fuel injectors.

If all of those components check out, move on to compression.

As @traildogck asked, why do you have one step colder plugs? You may want to check out your plugs even before swapping coils, since they may simply be fouled due to the non-optimal application.
 

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Discussion Starter · #6 ·
you might be able to borrow a boroscope,
off a parts store. (these things are really typical now, pro mechanics may have more then one).
Borrowed one from AutoZone today. The resolution isn't very good. The piston looks ok, but I can't see much. There is carbon, but I'm not sure what is too much.

Why the colder plugs?

You have to check the plug and gap.

Also check the coil plug quick connect. They are famous for fatiguing and not fully clicking in place or breaking off. You can actually zip tie them on (to keep pressure) if you can't get a replacement end. They are not hard to change. But you need a salvage harness or the proper new connector.

I have had misfiring issues from this before.

Do you have any drive-abilty issues? Idles wonky sometimes? Intake/Vacuum leaks?

Have you checked fuel pressure?

My plugs were usually fouling, rich. Spark NOT efficient. Gap, can affect spark efficiency.
One step colder plugs were recommended by my tuner.
NGK LFR7AIX

Checked for a 0.032 gap and it's looks ok.

Idles odd occasionally but runs fine in gear. I don't think there are any leaks but I'm not sure how to be certain. Boost and vacuum seem fine on my gauge, but for exhaust, I don't know.

Not exactly sure how to check fuel pressure for that one cylinder.

The procedure for diagnosing a single-cylinder misfire is as follows:
1. Swap the #1 & #3 ignition coils and see if the misfire follows. If so, replace the bad coil. If not,
1.5. On Subarus, the coil connector pins can get a little loose. Give them a tiny twist with needle-nose pliers to ensure the connection is snug. Assuming that doesn't do it,
2. Swap spark plugs. If those check out,
3. Swap fuel injectors.

If all of those components check out, move on to compression.

As @traildogck asked, why do you have one step colder plugs? You may want to check out your plugs even before swapping coils, since they may simply be fouled due to the non-optimal application.
One step colder plugs were recommended by my tuner.
NGK LFR7AIX

Going to swap some things.

It's odd. The code came on this afternoon and then I reset and drove to where I can work on it and the code didn't come back on. I can't reproduce it on demand.

Cyl 1 plug is in the image below.
 

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On the Super Mod Squad
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what do the other plugs and cylinders look like? vs. #1

and when putting th plugs back in don't forget a little antisieze.

only a "virgin" NGK plug goes in without it.

and 1 plug for checking the gaps. I watched a video from NGK a while back and the factory guy said any random plug or plugs can be bounced around in the factory boxes enough to be put out of spec for your car.

and recommended a gap checker like this one for iridiums (= modern plugs with more fragile tips then older types)

https://www.amazon.com/gp/product/B000CO9NSE/
 

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Discussion Starter · #8 ·
what do the other plugs and cylinders look like? vs. #1

and when putting th plugs back in don't forget a little antisieze.

only a "virgin" NGK plug goes in without it.

and 1 plug for checking the gaps. I watched a video from NGK a while back and the factory guy said any random plug or plugs can be bounced around in the factory boxes enough to be put out of spec for your car.

and recommended a gap checker like this one for iridiums (= modern plugs with more fragile tips then older types)

https://www.amazon.com/gp/product/B000CO9NSE/
Pulled the cyl 3 plug just now. Gap is ok and it looks similar to the cyl 1 plug as far as I can tell.
 

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On the Super Mod Squad
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are you logging with rom-raider? attach them here and post em up.

I wonder if the other 3 are in a similar condition but only #1 is bad enough to actually log a individual misfire.
 

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Discussion Starter · #10 ·
are you logging with rom-raider? attach them here and post em up.

I wonder if the other 3 are in a similar condition but only #1 is bad enough to actually log a individual misfire.
I have a Cobb AccessPort but I have been unable to have the code pop up while logging is on.

I've taken both the #1 and #2 injectors and spark plugs out and swapped them.

I took the OCV out as well. I sprayed it down with non-chlorinated brake cleaner, dipped it in fresh oil, and reinstalled.
 

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Discussion Starter · #12 ·
What mods do you have? Who is your tuner, and on what basis did he recommend the plug change?
Johnson Tuning / Fathouse Fabrications near Waverly, IN.
I don't recall the exact reason. I had it in a message but I've reset my phone since then.

Mod List:
Air Pump Delete
IAG Street Series AOS
AEM UEGO Wideband

Turbo/Intake:
Boost Controlled Performance BCP x400
GrimmSpeed TMIC

Exhaust:
Cobb Catted Downpipe

Fueling / Plugs:
Cobb Fuel Pump
Injector Dynamics 1000s
NGK LFR7AIX Plugs
 

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2005 Legacy GT wagon 5MT Limited
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Well, there you go. When asking for technical advice, you should definitely state up front that you have those mods - particularly the BCP X400, Cobb pump, and ID1000s. You've got substantial power upgrades that do in fact justify the one step colder plugs. They also affect the advice people should give you. If you receive and follow advice given under the assumption you have stock turbo & fueling, you could severely damage your engine.

OK, moving on - the mods do not affect the diagnosis procedure for the single-cylinder misfire; proceed with that.

Driving around with upgrades like that, you should really be able to monitor your car's general health/performance. I highly recommend an OBDLink MX dongle and the BtSssm app on an Android device. That'll give you great information all the time, and help out with debugging this one.
 

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Discussion Starter · #14 ·
Well, there you go. When asking for technical advice, you should definitely state up front that you have those mods - particularly the BCP X400, Cobb pump, and ID1000s. You've got substantial power upgrades that do in fact justify the one step colder plugs. They also affect the advice people should give you. If you receive and follow advice given under the assumption you have stock turbo & fueling, you could severely damage your engine.

OK, moving on - the mods do not affect the diagnosis procedure for the single-cylinder misfire; proceed with that.

Driving around with upgrades like that, you should really be able to monitor your car's general health/performance. I highly recommend an OBDLink MX dongle and the BtSssm app on an Android device. That'll give you great information all the time, and help out with debugging this one.
You're right, I really should put all that in my signature so it's there every time.

After swapping plugs and injectors from 1 and 3 the code has not come back, yet... (knock on wood). Trying to remember to log on the accessport each time I drive until I'm satisfied that the issue isn't going to return.
 

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Discussion Starter · #16 ·
Mind sharing how much power you're putting out? My brother (owns a WRX) makes fun of the idea of have a turbo charged Outback. I'm willing to bet your XT would destroy his car :grin2:
I had dabbled with the idea of getting a WRX or STi for awhile, but I already had an 06 2.5i Outback and liked having more storage and hauling space so I went for the Outback XT. 3rd gen for the win!
I didn't go all out on power. This is still my daily driver so I needed it to be reliable, but if I had spent a bit more and changed some things I probably could of had another 100whp. I'm still running the stock catback, too.

Dyno Chart Attached
 

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Dyno Chart Attached. I didn't go all out. This is still my daily and I needed it to be reliable, but if I had spent a bit more and changed some things I probably could of had another 100whp. I'm still running the stock catback.
Modified XT ...and reliable daily driver do not typically make it in the same statement.
( @traildogck has 2, ...only one is a daily driver,).
 

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Master Caster
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Modified XT ...and reliable daily driver do not typically make it in the same statement.
( @traildogck has 2, ...only one is a daily driver,).
Yeah, one is sitting in barn in Golden. Haha.

They just require lots of monitoring and attention once you mod past a certain point. They are no different than any other car. If you neglect maintenance and flog your Kia to redline everytime ... it's gonna blow up also.

As any car, you just need to use your head. Modified DD XT's just force you to use ... "more head". Wait, can I say "more head"?

Phrasing?
 

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After swapping plugs and injectors from 1 and 3 the code has not come back, yet... (knock on wood). Trying to remember to log on the accessport each time I drive until I'm satisfied that the issue isn't going to return.
Just cause you don't have a CEL doesn't mean the issue isn't there. You only pop a CEL if you hit 30 misfires per sampling period (I don't remember how long the period is, maybe 5 or 10 seconds). If you have an APv3, set up gauges for roughness on cylinders 1-4, and you can see every misfire detected. If you have an APv2, I highly recommend the OBDLink. If you see misfire counts > 1 per sampling period, you have a problem.

Unfortunately, by swapping both plugs and injectors without determining whether the misfire moved, you've just wasted all your effort.
 

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Discussion Starter · #20 ·
Modified XT ...and reliable daily driver do not typically make it in the same statement.
( @traildogck has 2, ...only one is a daily driver,).
Well if it breaks on my road trip to Denver next week, traildogck might have a 3rd in his driveway. lol

Yeah, one is sitting in barn in Golden. Haha.

They just require lots of monitoring and attention once you mod past a certain point. They are no different than any other car. If you neglect maintenance and flog your Kia to redline everytime ... it's gonna blow up also.

As any car, you just need to use your head. Modified DD XT's just force you to use ... "more head". Wait, can I say "more head"?

Phrasing?
More head, more better!
 
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