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Old 09-01-2021, 06:59 AM   #1
SwitchUps
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Default Misfire in Cylinder 1

Hello All,

I am getting a misfire in cylinder 1. I been monitoring cylinder roughness in that cylinder for a couple of months now. Highest I seen was like 66 roughness counts. Usually happens when car is cold and idling but can occur in low boost. Check engine light has come up a few times but it's not flashing. I had this for like a year now but car runs fine and no issues whatsoever. Last time I cleared the code it didn't come back for like 6 months. I replaced the spark plugs and replaced that coil pack but it just came back today. Any suggestions?

Next thing I'm going to do is go E85 and obviously get a new fuel pump and injectors, because I suspect the injectors maybe the culprit.

Car is just modded with intake and downpipe both Maperformance and I had this issue before adding both.

2015 STI Launch Edition. 77k miles and I am on Minnesota.
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Last edited by SwitchUps; 09-01-2021 at 07:50 PM.
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Old 09-01-2021, 07:21 AM   #2
Jay11STI
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I would recommend fixing the misfire issues before adding more mods and power to the car.

You can try swapping injectors to see if the misfire moves. Have you checked for air leaks yet?

It would help if you let everyone know what year, and model car with how many miles.
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Old 09-01-2021, 08:58 AM   #3
pigboat_2
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Location: Denver/ Eglin AFB
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Coil pack plug not fully seated?
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Old 09-01-2021, 09:16 AM   #4
Blackfin
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Chapter/Region: E. Canada
Location: Ontario
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2010 STi
Dark Gray Metallic

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You don't say what year the car is but if it's older and/or if you live and drive in a northern climate where road salt is used you might want to check the COP (coil on plug). Mine developed a misfire on #1 under moderate boost and it turned out the COP for #1 had developed some pretty serious corrosion on it laminations:

https://i.imgur.com/tPzC3M1.jpg

which no doubt crept into the coil itself and wrecked it.
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Old 09-01-2021, 12:20 PM   #5
JSR84
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White

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Compression and leakdown test.
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Old 09-01-2021, 07:51 PM   #6
SwitchUps
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Quote:
Originally Posted by Jay11STI View Post
I would recommend fixing the misfire issues before adding more mods and power to the car.

You can try swapping injectors to see if the misfire moves. Have you checked for air leaks yet?

It would help if you let everyone know what year, and model car with how many miles.
Yeah that would probably help lol. Added to post.
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Old 09-01-2021, 07:52 PM   #7
SwitchUps
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Quote:
Originally Posted by pigboat_2 View Post
Coil pack plug not fully seated?
I don't think that's the issue because I was having that problem before I put a brand new one in.
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Old 09-02-2021, 10:26 AM   #8
pigboat_2
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Well, I'd do a compression test then.
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