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Old 01-12-2021, 03:05 AM   #5
jimmy12345678
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Member#: 516695
Join Date: Jul 2020
Vehicle:
2008 Impreza 2.5i

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Thread Update

I filled the car up from 1/4 tank with 93 octane and drove it around for a day or so to make sure the gas is sufficently mixed in before recreating the driving conditions that made the problem occur before.

The higher octane fuel did NOT eliminate the rattling noise that occurs around 5k rpm under heavy load, so I don't feel that is it spark knock, although the car did seem to have less power at those rpm's, as if it was pulling timing to correct for spark knock. Also whenever the noise started it was accompanied by an "oil burning" type smell that even my girlfriend noticed and pointed out, I don't know if that helps at all but I thought I'd include it.

Based on my experience as a mechanic, I'm guessing I need to check valve lash and do a valve adjustment to see if that makes any difference, but I am not experienced with Subies, so what do you guys feel would be prudent to look at now that I've eliminated one of the potential causes? It's definitely some sort of engine noise.
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Last edited by jimmy12345678; 01-12-2021 at 04:59 PM.
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