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Old 11-16-2020, 10:31 AM   #1
Landyn_904
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Member#: 520319
Join Date: Nov 2020
Default Knock sensor going of on decel? Am just worrying?

I have an 09 wrx hatch with about 121k miles on it, recently it started to set off the knock sensor during decel, but it very seldomly does it. I understand that -1.4 to -2.8 degrees of knock correction on my accessport is ok, but it will go to -4.2 for a split second. Is this normal, if not should I be worrying?
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Old 11-16-2020, 11:08 AM   #2
rtv900
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Join Date: Aug 2015
Location: philadelphia
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2016 STI

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you're talking about feedback knock crap, not actual DAM
feedback knock shows up if you kick up a pebble, there is no way to drive a vehicle without getting those numbers
don't worry about them
And I mean hell, on Decel??? Obviously it is false knock. Pretty tough to have excessive cylinder temps and pressures pre spark when you are at full vacuum
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Old 11-16-2020, 12:04 PM   #3
Landyn_904
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Quote:
Originally Posted by rtv900 View Post
you're talking about feedback knock crap, not actual DAM
feedback knock shows up if you kick up a pebble, there is no way to drive a vehicle without getting those numbers
don't worry about them
And I mean hell, on Decel??? Obviously it is false knock. Pretty tough to have excessive cylinder temps and pressures pre spark when you are at full vacuum
The thing is, it's low in the rpm range, it will only do it after I did a pull and then I let it go to around 2k-ish rpm
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Old 11-16-2020, 12:37 PM   #4
Stretch18
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Join Date: Mar 2010
Chapter/Region: South East
Location: America's Penis
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2010 WRX
pandiculation

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Quote:
Originally Posted by Landyn_904 View Post
The thing is, it's low in the rpm range, it will only do it after I did a pull and then I let it go to around 2k-ish rpm
Probably just the resonation point for a loose heat shield or something. If you're engine braking, spark is turned off, so there isn't any concern about detonation, since there's not going to be any combustion energy to contend with.

A log might be helpful to confirm, but things start to get lose on older cars, so there's probably a bolt that needs to be tightened. I'd also had some ghost knock that corrected when I replaced my front wheel bearings, but never on deceleration...
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