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Old 09-08-2020, 12:27 AM   #1
Zeluhs
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2018 WRX STI
World Rally Blue

Default [SOLVED!] 18 STI misfire on boost no CEL

[SOLVED!] When ever I hit 5+ PSI of boost I get misfire, no CEL so I can't tell which cylinder it is. I've put in new cold NGK plugs gapped to .025 and it's still bad tuner suspects bad coils since the ARF readings are normal until boost, he think's because of weak spark but before I spend 400 on a new set of coils I did some resistance readings on every coil and got .8k ohms on the first and about 7K ohms on the second for every coil. I compared them to a AutoZone replacement coil and got readings of 1.2K ohms on the first and 4.5 on the second. I'm going to get a new OEM coil from Subaru tomorrow to see what it's readings are but I doubt all 4 of my coils are bad unless the AutoZone coil is closer to OEM which I doubt. What are y'alls thought?

Mods:
Type RA short block
TGV delete
1050 CC injectors
AEM 340 Fuel pump
Cobb FPR
Cobb Fuel pressure sensor
Cobb FlexFuel
AIG AOS
Catless downpipe
Muffler delete exhaust
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Last edited by Zeluhs; 09-20-2020 at 05:09 PM. Reason: solved
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Old 09-08-2020, 08:13 AM   #2
Haevn
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2011 WRX
WRB

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Have you checked for boost leaks
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Old 09-08-2020, 12:33 PM   #3
Zeluhs
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Quote:
Originally Posted by Haevn View Post
Have you checked for boost leaks
Yes tuner used a smoke machine and patched them all
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Old 09-10-2020, 10:14 AM   #4
Zeluhs
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World Rally Blue

Default Update

Quote:
Originally Posted by Zeluhs View Post
When ever I hit 5+ PSI of boost I get misfire, no CEL so I can't tell which cylinder it is. I've put in new cold NGK plugs gapped to .025 and it's still bad tuner suspects bad coils since the ARF readings are normal until boost, he think's because of weak spark but before I spend 400 on a new set of coils I did some resistance readings on every coil and got .8k ohms on the first and about 7K ohms on the second for every coil. I compared them to a AutoZone replacement coil and got readings of 1.2K ohms on the first and 4.5 on the second. I'm going to get a new OEM coil from Subaru tomorrow to see what it's readings are but I doubt all 4 of my coils are bad unless the AutoZone coil is closer to OEM which I doubt. What are y'alls thought?

Mods:
Type RA short block
TGV delete
1050 CC injectors
AEM 340 Fuel pump
Cobb FPR
Cobb Fuel pressure sensor
Cobb FlexFuel
AIG AOS
Catless downpipe
Muffler delete exhaust
Update New ignition coils have been installed and still misfires
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Old 09-11-2020, 03:42 PM   #5
kharmicresonance
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Pull your plugs and double check the gap?
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Old 09-12-2020, 12:50 PM   #6
Zeluhs
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2018 WRX STI
World Rally Blue

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Quote:
Originally Posted by kharmicresonance View Post
Pull your plugs and double check the gap?
I did when before I installed the new ones. Would it help to send a data log?
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Old 09-12-2020, 01:29 PM   #7
subaru_gc8
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silver

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so how do you know its a misfire? and did it misfire before the tune and other stuff?
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Old 09-20-2020, 05:09 PM   #8
Zeluhs
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Default Solved!

Quote:
Originally Posted by subaru_gc8 View Post
so how do you know its a misfire? and did it misfire before the tune and other stuff?
Figured it out, first tuner I went to is a massive moron. It was a massive boost leak from the turbo L pipe to the intercooler. No idea how they missed that but I will never be going back to them. Had to go to Dallas to see AWDTuning they know subies.
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