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Old 10-28-2020, 11:16 PM   #1
S-Tecnica-I
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Default Closed Deck/Speed Density - Misfire

Hello my friends. Hoping you guys might have some ideas or direction.


Brand new closed deck, 1400+ miles. Just switched to speed density and new tune of course. I am now getting misfire codes...(never had these codes before this SD setup) Latest being P0000 P0300 P0302. Previously, had misfire codes as well as exhaust cam codes.


I reset the first time and drove car with no additional codes. Care drove strong. 2 days later, I received the codes listed above. I reset again and drove and car drove strong.


Both times was shortly after startup. I noticed that cold startup on both occasions was really rough and then smoothed out. Codes came on during the short low speed drive out of development. Both times, I pulled over a short time after to reset and never saw the codes during those drives.


Any thoughts???


Thanks All!
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Old 10-29-2020, 12:10 AM   #2
alexmartynyuk
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What cams and are you still running avcs?
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Old 10-29-2020, 01:32 AM   #3
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Quote:
Originally Posted by alexmartynyuk View Post
What cams and are you still running avcs?

Factory heads were refurbished with new block, but OEM.
I assume yes on AVCS. Was never discussed.
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Old 10-29-2020, 11:20 AM   #4
BeastianSTI
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What else has changed? Bigger injectors? Were the injectors cleaned while the engine was apart?

New spark plugs? What are they gapped to?

Speed density isn't > MAF based necessarily. When I switched to SD, I noticed misfires as well.
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Old 10-29-2020, 11:55 AM   #5
S-Tecnica-I
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Quote:
Originally Posted by BeastianSTI View Post
What else has changed? Bigger injectors? Were the injectors cleaned while the engine was apart?

New spark plugs? What are they gapped to?

Speed density isn't > MAF based necessarily. When I switched to SD, I noticed misfires as well.

Nothing. New plugs with new block. Same injectors ive been using with previous block (about a year old)



You noticed misfires? So you still "notice" them or was it resolved?
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Old 10-29-2020, 12:17 PM   #6
subaru_gc8
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so what I would do is if you can go back to the stock tune run that for a while if the misfires are tune dependant than you know whats causing it. if not i would look into the coils
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Old 10-29-2020, 12:24 PM   #7
S-Tecnica-I
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Quote:
Originally Posted by subaru_gc8 View Post
so what I would do is if you can go back to the stock tune run that for a while if the misfires are tune dependant than you know whats causing it. if not i would look into the coils

So go back to MAF tune?
As stated, no misfires before SD setup. SD=bad coils???


FYI - For now this appears to be a cold start issue. Idle hunt is terrible during warm up. Codes appear shortly after. Not sure if this helps those who might know or have experienced this issue.
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Old 10-29-2020, 01:29 PM   #8
BeastianSTI
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Quote:
Originally Posted by S-Tecnica-I View Post
So go back to MAF tune?
As stated, no misfires before SD setup. SD=bad coils???


FYI - For now this appears to be a cold start issue. Idle hunt is terrible during warm up. Codes appear shortly after. Not sure if this helps those who might know or have experienced this issue.
I'd recheck the spark plug gap too, just to be sure that's not causing you any problems. Torque them to spec using a torque wrench, of course.

My cold starts on e85 are pretty bad. 1 of every 4 times I start it, the car stumbles for about 30s but eventually picks back up fine.

What IAT / MAP sensor did you end up going with? Barring that, I'd ask your tuner what's going on.
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