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2004 X AWP
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75 Posts
Discussion Starter #1
Will a failing knock sensor always throw a CEL? I still suffer from knock in my 04 SG N/A, there has never been a CEL shown, but it is becoming more obvious that knock is the problem.

Nick
 

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03X MT
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846 Posts
not sure sure of your actual condition but if your "knock" is there only when warming the engine do a search "piston slap"
 

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2004 X AWP
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75 Posts
Discussion Starter #3
The 'knocking' is in fact pre-detonation, which i presume a correctly functioning 'knock sensor' would detect and allow the ECU to adjust accordingly. There are no issues with piston slap as far as i'm aware, as the noise is associated with light throttle application and mid range RPM.
 

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2015 Forester X 6MT 6-Gear Manual
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1,373 Posts
Knock sensor wont hear "pinging" only knocking - BIG BIG difference. Dirty combustion chambers and too hot plugs will exacerbate this issue. You dont want your ecu retarding ignition timing when it doesnt have to - that'll start a downward performance spiral - MORE carbon, MORE knock. Maybe its past due for a water injection steam clean of the chambers. I think there are a couple thread on that ...
 

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2014 328i xDrive Wagon 8 spd Auto
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..... Maybe its past due for a water injection steam clean of the chambers. I think there are a couple thread on that ...
I'd never heard of that before (along with lots else I've never heard of) but I'm wondering just how they do that and how tough it is on the engine?
 
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