What is this and why??

1

12lepler

Member
Joined
Dec 27, 2013
Ok. So I have a knock gauge in my modded 1986 GN. It's got a green section of leds, a yellow section of leds and a red section of leds. It's never been of much help. It's never been of much help because first I don't know for sure how to read it. and second, it will be whatever random color it feels like when I start it. I start it and sometimes it's green, then most times I start it and it's in yellow, sometimes it'll be In red. And you think when it's in red I would hear knocking, but no matter where the gauge is at, the car runs the same. I asked the previous owner, (who isn't really that big into modding cars, he bought the car modded) how this knock gauge worked, and he said "oh it never really did anything. I was told it ran off something on the driveshaft" So I was doing some looking around because what he said makes no sense. And I found this.... does this look like a knock sensor to you guys?? And if so.. why is it back here?

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12lepler said:
Ok. So I have a knock gauge in my modded 1986 GN. It's got a green section of leds, a yellow section of leds and a red section of leds. It's never been of much help. It's never been of much help because first I don't know for sure how to read it. and second, it will be whatever random color it feels like when I start it. I start it and sometimes it's green, then most times I start it and it's in yellow, sometimes it'll be In red. And you think when it's in red I would hear knocking, but no matter where the gauge is at, the car runs the same. I asked the previous owner, (who isn't really that big into modding cars, he bought the car modded) how this knock gauge worked, and he said "oh it never really did anything. I was told it ran off something on the driveshaft" So I was doing some looking around because what he said makes no sense. And I found this.... does this look like a knock sensor to you guys?? And if so.. why is it back here?

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Click to expand...

That is not a knock sensor. Ill look at it again after this post, but I am not sure what it is. If the knock gauge is showing red DO NOT STOMP ON IT! The motor is knocking. You can't hear it! You are going to learn how to change a head gasket really soon. The knock sensor is located behind the intake on the motor. It detects the pinging inside the motor. The computer will attempt to pull timing to save the motor... Get a scanmaster!
 
google yourself a pdf file if you need to read up on the gauge...or go to caspers electronics site. I however suggest you just use your scanmaster to monitor the knock. what the heck is that thing by the driveshaft:confused:
 
ZNix said:
That is not a knock sensor. Ill look at it again after this post, but I am not sure what it is. If the knock gauge is showing red DO NOT STOMP ON IT! The motor is knocking. You can't hear it! You are going to learn how to change a head gasket really soon. The knock sensor is located behind the intake on the motor. It detects the pinging inside the motor. The computer will attempt to pull timing to save the motor... Get a scanmaster!
Click to expand...

I got the car 2 weeks ago and I've put about 300 miles on it. (250 of those were the drive getting it home). And as I dig into this car, I find more mods and more little annoying problems. The car IS going to sit for a while until I get everything sorted. I bought the car because It only has 51k miles, and It's totally rust free. I'm getting a Scanmaster soon, and I have NOT stomped on it yet because I don't trust anything on the car. I also wanna get a TT chip because I wanna be sure the tune it's running is safe. It has some no name chip in it now and I really want it gone. The problem i have with this knock gauge is.. I don't trust it. Shouldn't it be adjusting as I drive? I'll drive and no matter what I do, it'll stay in the same color. I'll start it and it will be in the middle of yellow. I'll stop and start it again and it'll be in green. Sometimes I start it and it's in red, so I just turn it off and start it again until it's not in red anymore. I don't get it. is it supposed to be that the farther towards red it goes, the more timing it's pulling?

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I think the gauge is broke. If you wire a push button switch in line you can just reset it. Call Caspers and ask John what to do. Maybe he will exchange it for you. Are you sure it is wired to that thing in your picture? If you run a carfax maybe you can locate the previous owner(s) and ask them.
 
GNRick said:
I think the gauge is broke. If you wire a push button switch in line you can just reset it. Call Caspers and ask John what to do. Maybe he will exchange it for you. Are you sure it is wired to that thing in your picture? If you run a carfax maybe you can locate the previous owner(s) and ask them.
Click to expand...

And that's probably a good idea about the car fax. I saw one when I bought the car but I lost it. It looks like at one point the motor was opened up. Idk what the thing has on the inside and I would sure like to know.

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Ok so can we assume the knock sensor is not wired to the driveshaft speed sensor?
 
The driveshaft thing could be for an aftermarket cruise control if your car doesn't have a factory cruise.
There is supposed to be a magnet mounted on the drive-shaft with a cable tie.
It looks like no magnet is there.
I don't have a knock guage but I thought it is supposed to be hooked up to the stock
knock sensor. If you have other noise like lifters knocking piston slap etc., maybe that's
causing the guage to flash different colors.
 
My knock gauge will show yellow or red when the starter engages the ring gear. After it starts it returns to green.
 
cork said:
My knock gauge will show yellow or red when the starter engages the ring gear. After it starts it returns to green.
Click to expand...

Mine starts green, then when I start it, it'll move up through the colors and stay at whatever color it gets to. It NEVER comes back down.

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12lepler said:
Mine starts green, then when I start it, it'll move up through the colors and stay at whatever color it gets to. It NEVER comes back down.

Posted from the TurboBuick.Com mobile app
Click to expand...
Sounds like it's not working correctly, I thought you just meant it was changing colors while the starter was engaged. It should return to green and only go to yellow or red as the knock sensor detects knock. Is the sensor plugged in ? It's on the very back of the block under the coil pack.
 
Again, you had to wire in a push switch on some of the older ones to reset it. I think you would normally cut into the black (neg.) wire but I'm sure someone will correct me if I am wrong.
 
I have a very similar Knock Gauge, I have not had the time to hook it up yet but according to the paperwork it should be wired to the cars computer to "hear" if knock is occurring. I am not sure if yours is the same but it maybe something to look into. Just an Idea.

Cam
 
I like my old school knock gauge easy to see during high speed passes in 5 years and 20-25 lbs of boost I have never had to replace head gaskets ! Any time it climbs to the last yellow I get off the throttle when they work they are pretty accurate of course there are variables with fuel delivery,octane,timing and boost it's a simple gauge that has saved my engine many times


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