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Old 07-24-2013, 07:59 PM   #1
Pickler
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Default please help, engine knocks bad at ~2500rpm

Hi guys I have a 2009 impreza 2.5i auto with only 40k miles on it. I do all the service and maintenance regularly including Spark plugs (ngk laser platinum). Anyway according to my logs engine knocks bad between 2000-3000rpm under heavy load (full throttle). So much so that IAM drops to zero and engine pulls as much timing as possible which often leads to poor low end power (more like non existent power). BUT I don't hear any knocks or pings. Once I had bad gas in there and I heard some pinging but after that no more. Even still my car pulls timing and reports knocks. my car does have a noisy heatshield/exhaust at low RPMs in hot weather. Am I a victim of false knock? I use premium gas only and car is stock.
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Last edited by Pickler; 07-25-2013 at 11:22 PM.
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Old 07-25-2013, 11:18 PM   #2
Pickler
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bump...
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Old 07-26-2013, 02:58 AM   #3
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You're still under warranty, so I'm going to say take it to a dealer.
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Old 07-26-2013, 07:11 AM   #4
Pickler
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will the dealership accept data logs? how am I going to prove knocking if its not audible?
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Old 07-26-2013, 08:39 AM   #5
Patrick Olsen
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Tell them you can feel the car hesitating, like it's pulling timing around 2500rpm.

Have you datalogged any other, similar cars to see how they behave?
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Old 07-26-2013, 08:58 AM   #6
Pickler
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Quote:
Originally Posted by Patrick Olsen View Post
Tell them you can feel the car hesitating, like it's pulling timing around 2500rpm.

Have you datalogged any other, similar cars to see how they behave?
yes but that was an acura. it had no issues with knocks despite 15 psi of boost and it built timing slowly but gradually up to redline (no dips or spikes in timing). this car I have been feeling hesitations at 2500 rpm for years. just didnt know what was wrong with it until I got a tactrix cable, and notice knock retards at those exact engine speeds. Dealership always claims the car is fine. This morning on the drive to work while climbing a small hill at 2500rpm timing dropped to 0 degrees. This was with a rich AFR mixture too.

Last edited by Pickler; 07-26-2013 at 09:05 AM.
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Old 07-26-2013, 09:34 AM   #7
Patrick Olsen
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I think you missed the bit about "similar" - an Acura with an aftermarket turbo setup is not similar to your N/A 2.5i.

So, let me be more specific - have you datalogged another N/A Subaru?
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Old 07-26-2013, 09:45 AM   #8
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oh sorry but thats why i said 'but' it was an acura lol. and it was factory turbo just over boosted (rdx). I have never seen logs of other NA subarus. seen plenty of turbo subaru logs though. I actually would love to see a log of na subarus on pump gas doing some pulls.
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Old 07-26-2013, 09:49 AM   #9
skyx39
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They can read the ECU and see that the IAM has dropped and any learned knock correction values. They won't need your datalogs if it has been knocking that much.
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Old 07-27-2013, 11:24 AM   #10
Pickler
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well I just took it to dealer and they dont know what im talking about when I mentioned the IAM.
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Old 07-27-2013, 12:43 PM   #11
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well I just took it to dealer and they dont know what im talking about when I mentioned the IAM.
They might use a different acronym, but they'll be able to tell of the timing is consistently being pulled. If they seem confused find a new dealer.
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Old 07-27-2013, 01:54 PM   #12
Pickler
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Quote:
Originally Posted by skyx39 View Post
They might use a different acronym, but they'll be able to tell of the timing is consistently being pulled. If they seem confused find a new dealer.
that's what i'm doing, i'm looking for a new dealership but there are not much around here. They took my car for a drive and came back saying no knock was present. Went home, hooked up my data logger and instantly read that IAM was at 0.
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Old 08-01-2013, 04:14 PM   #13
djemzine
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Not to worry I am in the same boat, and you can use my car by testing it out with the data logger.
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Old 08-01-2013, 11:41 PM   #14
Pickler
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Quote:
Originally Posted by djemzine View Post
Not to worry I am in the same boat, and you can use my car by testing it out with the data logger.
well i told you yours doesn't ping! nice meeting you today
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Old 08-02-2013, 05:18 PM   #15
NH8991
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As i've mentioned in other threads, i'm a big advocate of running higher octane gas (at least in my car - 09 2.5i 4EAT), running 89 or 91 (even when it was stock) certainly smoothed out the lumpy feeling it had at low revs under high load (e.g uphill in top gear). I wasn't logging the car back then so I can't comment whether it was pulling timing or not.

Even if you are stock, I definitely recommend getting a tune.
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