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Old 01-15-2013, 04:58 PM   #26
WheelsCSM
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Join Date: Jul 2002
Chapter/Region: RMIC
Location: Arvada, CO
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2008 Forester XT
6mt/18g-xt

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I have been chasing false knock on my Forester ever since I rebuilt the engine last March. I have done boost leak and compression tests, run octane boost, and adjusted timing in cells with no real help or change. The only thing I'm left with its a bad knock sensor or something loose in the engine bay. I have found a couple loose items in the engine bay, but still does it.

The only things I have found that helped are to adjust the thresholds that the knock sensor is active, from .65 to .85, and lower the max fbkc to -6. Most of mine occurs below.85, but I still occasionally get it at higher loads. I get almost no knock at wot runs-probably because I just pulled 1-2 deg across the map.

There does seem to be some correlation between driving on rough roads or bumps and getting lots of knocks, but it is not consistent and I have been through the engine bay so many times I don't know what could be causing it.

I don't like it, but I'm tired of pulling my hair out trying to fix it. Only thing that makes me feel better is that with over 15k miles on the rebuild, compression has not changed.
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Old 01-16-2013, 09:09 AM   #27
bmx045
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2011 MCS

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be careful with how much timing you pull, too little is bad as well.
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Old 01-16-2013, 09:12 AM   #28
Nickcrsx
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Quote:
Originally Posted by bmx045 View Post
be careful with how much timing you pull, too little is bad as well.
This is the interesting fact...

The car is currently running on the base timing maps due the FBKC. This could also be why I am feeling massive bucking, hesitation...

Injectors are cleaned and going back in tonight.

Wish me luck
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Old 01-16-2013, 10:44 AM   #29
NoGraffix
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Chapter/Region: MWSOC
Location: Windy City
Vehicle:
I am Rub
Function>Form

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So did you ever get the knock sensors checked out (and likely replaced)?


Also FYI those brackets over the injectors are ****ing stupid. I cut those off as soon as I decided to swap my injectors. The rails do have some play and can be bent, just gotta make sure you didn't crack them. If you did you'll know as soon as you turn the key and the fuel pump primes, fuel will be splattering all over the place.
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Old 01-16-2013, 05:12 PM   #30
Nickcrsx
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Just to confirm. 17.4ft-lb is 208.8 in-lb?
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Old 01-19-2013, 09:04 AM   #31
Nickcrsx
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Okay guys. After 3 days of wrenching (did it little by little) I checked the following:
-plugs and they look perfect
-injectors professionally cleaned
-compression test -130psi across all 4 cylinders
-re-torqued knock sensor to specs.

I seem to have developed a small vac leak somewhere I need to trace but I suspect it's coming from the bottom of one of the injectors. Anyways. My problem still persists.

Short of lighting this car on fire I think I am done and I'm throwing in the towel.
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Old 01-19-2013, 11:49 AM   #32
MaddMax
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I think you have a minor vacuum leak that may only pop up as the motor pulls around in it's mounts. I'd test the vacuum (engine warm) and make sure it's steady and in spec. I'd also remove the entire intake tract and intake manifold, check everything closely, and reinstall carefully.

I'd also replace the knock sensor or at least remove it and check the wiring harness as sometimes that's the culprit for a failed sensor.
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Old 01-23-2013, 04:37 PM   #33
Nickcrsx
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edited.

Last edited by Nickcrsx; 03-06-2013 at 04:24 PM.
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