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Knock Sensor Newb.

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Long Duk Dong

10+ Year Contributor
126
0
Jul 8, 2008
Montgomery, Alabama
Just a short knock sensor write up for us newbs - Everyday I am learning new and interesting stuff about these cars. Most recently, I discovered that I was picking up what appeared to be a good deal of "knock" even on start-up. At first I attributed this to the installation of the poly motor mounts. After checking the knock sensor a little closer I found that the previous owner had removed the knock sensor and filled it with some type of sealant. I assume it was because it was old, leaking and that he was looking for a cheap fix. After getting a copy of ECM link I also discovered that the intermittent engine code that was popping up was a “0031” – Faulty Knock Sensor. I also noticed that no matter how good I had the numbers looking in the data log it would still knock at times causing me to question item after item. As such I ordered a Beck Arnley knock sensor from one of the local parts stores.

Before installing it I did some research both here and on the ECMLink forums. I discovered two things – One, DO NOT over tighten the knock sensor. That issue alone can cause one a great deal of headache by causing the knock sensor to pick up what is referred to as “False knock”. Apparently the gent I bought it from either A) didn’t care or B) didn’t know as it was VERY tight. A dab of Locktite and a slight nudge over hand tight seems to be the trick. It is easily accessible with the car on a lift as it is located below the intake manifold, on the back side of the engine block, slightly offset towards the drivers side from the center. It can be done with relative ease with the car in the air. Just make sure to use JACK STANDS if you use a jack so you don’t flatten yourself in the event of a jack failure. Flat DSM'er's aren't any good unless served up with syrup. I installed the new one and wallaa, it now runs and idles like new money with no codes and my logs look MUCH, MUCH BETTER. This may or may not be redundant but I hope that it will help someone as new to the DSM world as I. :D
 
Note - Running Link or another suitable tuning solution will allow you to deactivate the knock sensor under a certain throttle position and RPM. I currently always set mine for 3000rpm-ish and 35%-40% Throttle as this is about the only time I ever got on it - well above these intervals.

Phantom knock is certainly something that will throw you off, you just have to pay attention and keep your eyes open for the signs which decipher what it Real knock and what is Phantom knock.
 
Last edited by a moderator:
Note - Running Link or another suitable tuning solution will allow you to deactivate the knock sensor under a certain throttle position and RPM. I currently always set mine for 3000rpm-ish and 35%-40% Throttle as this is about the only time I ever got on it - well above these intervals.

Phantom knock is certainly something that will throw you off, you just have to pay attention and keep your eyes open for the signs which decipher what it Real knock and what is Phantom knock.

what is phantom knock?
 
thanks for this.

Glad to help. :D

what is phantom knock?

“Phantom knock” can be caused by a multitude of things. I have run into this on Grand Nationals and LS1 cars (Not as much with LS based cars. I work on them ALLOT.). It is a situation where the knock sensor is picking up a frequency that it believes to be pre/post detonation, a rod knock or the like when in all actuality it isn’t knock at all, but more-so some other type of noise. It can be caused by things such as an automatic trans shift that is "noisy", clutch issues in a standard shift, bad balancer, excessive accessory noise, loose items bolted to the engine; etc. These are but a few of the ones I have run into. I am sure there is much more that could be added. :D
 
Glad to help. :D



“Phantom knock” can be caused by a multitude of things. I have run into this on Grand Nationals and LS1 cars (Not as much with LS based cars. I work on them ALLOT.). It is a situation where the knock sensor is picking up a frequency that it believes to be pre/post detonation, a rod knock or the like when in all actuality it isn’t knock at all, but more-so some other type of noise. It can be caused by things such as an automatic trans shift that is "noisy", clutch issues in a standard shift, bad balancer, excessive accessory noise, loose items bolted to the engine; etc. These are but a few of the ones I have run into. I am sure there is much more that could be added. :D

is there a way to make the knock sensor not so sensitive? Although i though the knock sensor only pick's up noises in the block not the engine compartment.

i would think phantom knock is a faulty knock sensor or a too tight/loose knock sensor.
 
oh how did you get the intermittent code to show up?
i'am using ecmlink v3 for 1g. I hear that you can't get the code to show unless it is on all the time.
 
oh how did you get the intermittent code to show up?
i'am using ecmlink v3 for 1g. I hear that you can't get the code to show unless it is on all the time.

If a code is displayed it should be stored in the DTC display even if it the "check engine" light has gone out so long as you haven't cleared the DTC's from what I can tell. If memory serves me right, on my daughters car the "check engine" light can on then went out. However, when I pulled up the DTC's it showed the "0031" code even though it wasn't currently displayed. I believe it stores it in the memory until it is cleared. Again this is from memory.

As for the knock sensor being less sensitive this is what I have found. At one point I used a small amount of teflon tape. It worked as a buffer and appeared to make the knock sensor less prone to pick up the hard shifts on my Grand National. Hope this helps ya bro. :D
 
hahahha!!!! i will fix this tommarow to see if thats what i did wrong..do you know a spec for it? i know i over did it for sure. been having knock issue from the first run after the build. god i hope this is the issue!
 
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