Question: Knock Sensor

[John Robinson]

I am wondering if anybody has mounted a knock sensor in a more accessible place other than the block. I have heard that you can mount it to an engine mount or any other bracket that is connected to the engine. My thinking is that this would be an easier way to replace the knock sensor by just leaving the one in the block and mounting a new one out in the open. All I am looking for is to give the ECM a signal that it will be happy with as far as the knock sensor is concerned.

 

[toptechx6]

I would have to question the wisdom of moving the knock sensors, particularly because the FSM indicates that even adding more sealer to the threads can degrade the signal. Just my take, I'm not an engineer, just an old grease monkey.:L

 

[vetteoz]

All I am looking for is to give the ECM a signal that it will be happy with as far as the knock sensor is concerned.

If you are going to go to that much trouble ; may just as well install the correct resistor that makes the ECM "think " a KS is present

 

[John Robinson]

If you are going to go to that much trouble ; may just as well install the correct resistor that makes the ECM "think " a KS is present

Can you tell me more about this resister and were it goes?

 

[Hib Halverson]

Do not relocate the knock sensor. Any change in its location will degrade the action of electronic spark control which is necessary to keep the engine out of detonation.

Ignore suggestions to replace the KS with a resistor unless you are willing to take the consequences of the engine controls' operating without the protection from detonation EST offers.

 

[boomdriver]

Do not relocate the knock sensor. Any change in its location will degrade the action of electronic spark control which is necessary to keep the engine out of detonation.

Ignore suggestions to replace the KS with a resistor unless you are willing to take the consequences of the engine controls' operating without the protection from detonation EST offers.

Man, do I agree with that !


Are you sure you want to remove the thing that protects the engine from certain death?

That knock sensor keeps your engine from scattering itself and its fragile aluminum pistons. I have first hand experience with this. I lost a piston to excessive knocking in another motor.
There is NO better way to manage engine knock than to instantly retard the timing,. That ends it right now. It happens so fast that the driver never even knows there is a problem with knocking. The ESC retards timing on the first "knock" the sensor feels.
The knock sensors signal is so precise that applying more than the reccomended torque to the sensor will distort its signal and the car can run poorly due to ign timing being off. As tech noted, even thread sealer or teflon tape has to be used with caution. Because water carries vibration so well, the sensor being in a water passage is the perfect place to "sense" piston knock since the cylinders are surrounded by water.

 

[aklim]

I am wondering if anybody has mounted a knock sensor in a more accessible place other than the block. I have heard that you can mount it to an engine mount or any other bracket that is connected to the engine. My thinking is that this would be an easier way to replace the knock sensor by just leaving the one in the block and mounting a new one out in the open. All I am looking for is to give the ECM a signal that it will be happy with as far as the knock sensor is concerned.

Can I ask why you want to do that? After all, how often do you play with the KS? It isn't like you change it every 3000 miles is it? Screwing with it might be bad. Just because you find a location that YOU like doesn't mean the ECM will. It is set to the harmonics at that position and moving it could make it over stimulated or under stimulated. Both are bad. If it is over stimulated, you will be pulling out timing where it shouldn't. If it is under stimulated, you could be knocking but it won't take out timing like it should and damage the engine.

Think of it like a woman. If she over stimulates you, you get done before you have had enough fun. If she under stimulates you, you get bored.

 

[aklim]

I would have to question the wisdom of moving the knock sensors, particularly because the FSM indicates that even adding more sealer to the threads can degrade the signal. Just my take, I'm not an engineer, just an old grease monkey.:L

I'm not a gynecologist but I do give free breast exams and other exams on a PRN basis.

 

[aklim]

If you are going to go to that much trouble ; may just as well install the correct resistor that makes the ECM "think " a KS is present

And what is going to retard the timing as necessary should there be light knock? Even if it doesn't damage the engine too much, pre-ignition is not good for power. Kinda like a "minuteman". Girl isn't happy and she might not ask him back again.

 

[John Robinson]

Can I ask why you want to do that?

My reason for asking this question is being prompted by the fact that for the last 10 months I have been chasing problems with the wiring and sensors. The knock sensor was found to have a bad wire to it and in order to fix it I had to crawl under the car and try to rewire the sensor. Now the problem is that the sensor wire connector has started to fall apart and I am getting code 43 - 55 - 63 -64. I believe the other codes will take care of there selves if the knock sensor is not screwing with the ECM from bad connections or sensor. Here is where it gets interesting for me I have kept this car because it is my only form of fun. I know you younger people are saying well it 's not that hard to do a knock sensor etc. First try being on fixed income since 1991. This year I have replaced the left half shaft joints myself in order to retain the fun of having something I can enjoy. As for doing the work myself it is getting harder for me to do the crawling under and over the car since I have had four heart surgeries, I have kidney failure, Diabetic, Congestive heart failure. Adding to that is the fact that I lost my health insurance from my retirement. So now you can see that in order for me to have some Independence and fun I have to find ways to keep my car running without having to buy a lot of expensive parts and I also have to find ways to make it so I can do the work myself. This thread was an effort for me to see if I could use a knock sensor from a junk engine with out laying under the car trying to put it in. As for the damage from detonation I am not as worried about that as I am about what is happening to my valves and pistons from running lean for almost a year.

At this point I am going to try to find out what the ohms for the sensor are supposed to be and will be putting a resister on the knock sensor wire.

 

[aklim]

This thread was an effort for me to see if I could use a knock sensor from a junk engine with out laying under the car trying to put it in.

As for the damage from detonation I am not as worried about that as I am about what is happening to my valves and pistons from running lean for almost a year.

The short answer is you can and it will fool the ECM into thinking there is something there but either way, you have to fix the wiring. Better to do it right the first time than to fix it more later. I have learned that over the years when I make a quick and dirty fix and it comes apart later on at the worst possible time.

You know that detonation also causes engine problems and you cannot hear them until it is way too much, right?

 

[toptechx6]

Can I ask why you want to do that?

My reason for asking this question is being prompted by the fact that for the last 10 months I have been chasing problems with the wiring and sensors. The knock sensor was found to have a bad wire to it and in order to fix it I had to crawl under the car and try to rewire the sensor. Now the problem is that the sensor wire connector has started to fall apart and I am getting code 43 - 55 - 63 -64. I believe the other codes will take care of there selves if the knock sensor is not screwing with the ECM from bad connections or sensor. Here is where it gets interesting for me I have kept this car because it is my only form of fun. I know you younger people are saying well it 's not that hard to do a knock sensor etc. First try being on fixed income since 1991. This year I have replaced the left half shaft joints myself in order to retain the fun of having something I can enjoy. As for doing the work myself it is getting harder for me to do the crawling under and over the car since I have had four heart surgeries, I have kidney failure, Diabetic, Congestive heart failure. Adding to that is the fact that I lost my health insurance from my retirement. So now you can see that in order for me to have some Independence and fun I have to find ways to keep my car running without having to buy a lot of expensive parts and I also have to find ways to make it so I can do the work myself. This thread was an effort for me to see if I could use a knock sensor from a junk engine with out laying under the car trying to put it in. As for the damage from detonation I am not as worried about that as I am about what is happening to my valves and pistons from running lean for almost a year.

At this point I am going to try to find out what the ohms for the sensor are supposed to be and will be putting a resister on the knock sensor wire.

Very sorry to hear about your health issues John, I can certainly appreciate how difficult this must be.
Unfortunately I don't think the resistor solution will work to cure your problem.
Your problem may be caused by wiring, but codes 55, 63, and 64 could also be caused by problems in the fuel system, if the fuel system is solid, the problem is more likely in the O2 circuit, good luck.

 

[John Robinson]

I have put in a new fuel pump actually a replacement for the one I had that sprung a leak in the pump housing. New filter, removed the screen in the fuel pressure regulator per FSM New pick up screen and the pressure is 47# at idle and at 2000 RPM it is 39# the injectors all check 12.6 ohms. The MAP has been replaced and the solenoid to the EGR was found to be bad. I have found vacuum leaks in the evap system that I have resolved and am now staring at the knock sensor as the source of my problem. I bought the car with 67K on it 2004 and it now has over 1o8K and it was giving code 43 when I f first bought it but they stopped after I tightened up the muffler brackets the mufflers no longer are banging around under the car.

 

[aklim]

it was giving code 43 when I f first bought it but they stopped after I tightened up the muffler brackets the mufflers no longer are banging around under the car.

That could make sense from the standpoint that you were receiving more knocking that it could possibly be and the ECM thought that the KS was malfunctioning.

 

[toptechx6]

I have put in a new fuel pump actually a replacement for the one I had that sprung a leak in the pump housing. New filter, removed the screen in the fuel pressure regulator per FSM New pick up screen and the pressure is 47# at idle and at 2000 RPM it is 39# the injectors all check 12.6 ohms. The MAP has been replaced and the solenoid to the EGR was found to be bad. I have found vacuum leaks in the evap system that I have resolved and am now staring at the knock sensor as the source of my problem. I bought the car with 67K on it 2004 and it now has over 1o8K and it was giving code 43 when I f first bought it but they stopped after I tightened up the muffler brackets the mufflers no longer are banging around under the car.

Sounds like you have covered most of the bases on the fuel system, the only thing I see remaining is injectors themselves. The resistance check only verifies the coil is within specs, the injectors could still be partially clogged and fail to deliver enough fuel.
I too had the code 43 in my 93, testing the circuit showed 5 volts at the sensors and resistance of the sensors was within specs, because of that I figured it must be caused by bad wiring or poor connection at the sensors. I replaced the connectors to both sensors without success. I finally replaced both knock sensors and have never seen the code return. What I did notice is that even though resistance of both sensors was within spec, there was quite a bit of variation between the two, I have no idea if that was the the root cause.
I have a set of stock injectors that I removed to install a set of Bosch III's, the only issue I had was long crank time when the car was hot, they showed no leaks with the rail removed from the manifold and pressure applied to the rail, however the Bosch III's did cure the long crank time hot.
I will send you the set at my expense if you would like to try them to help isolate your problem. If you determine your injectors are the cause I would suggest purchase of the Bosch III's from Jon and simply ask you to return mine. PM me with a shipping address if you are interested, changing injectors on an LT1 is as easy as it gets, shouldn't take more than an hour tops and everything is up top, no crawling under the car required.

 

[aklim]

I too had the code 43 in my 93, testing the circuit showed 5 volts at the sensors and resistance of the sensors was within specs, because of that I figured it must be caused by bad wiring or poor connection at the sensors. I replaced the connectors to both sensors without success. I finally replaced both knock sensors and have never seen the code return. What I did notice is that even though resistance of both sensors was within spec, there was quite a bit of variation between the two, I have no idea if that was the the root cause.

I have a set of stock injectors that I removed to install a set of Bosch III's, the only issue I had was long crank time when the car was hot, they showed no leaks with the rail removed from the manifold and pressure applied to the rail, however the Bosch III's did cure the long crank time hot.

I think it could be that one sensor degrades and gets lazy. Kinda like the O2 sensor.

WTF!! I have had that problem. I will be sending my injectors to John to test.

 

[John Robinson]

toptech
Thank you for the offer of the injectors. I will keep that in mind but first I want to just put a resister on the right bank knock sensor. I was just out looking for the common wire in my case dark blue wire from both knock sensors to the ecm connector. It occurs to me that if I only put a resister on the ks that the electrical connection has turned to dust I will still have one working sensor so the impact of the ecm not being able to retard the spark should not be as bad as if I disable both ks in effect I would have only removed one half of the sensors. I can see why most people would put the resister in the wire close to the ECM because it is so easy to get to but when they do that they do remove all ks protection because that wire is the common wire for both sensors. What are your thoughts on this thinking. I also was thinking that I could have an injector that was intermittent in how it works causing the code 64 Lean 02 sensor on right bank.

 

[vetteoz]

That knock sensor keeps your engine from scattering itself and its fragile aluminum pistons.

I will play devils advocate.
While not disputing the reason for the existence of the KS , for those of you old enough to remember; in the good 'ole days, the hot tuning trick for street engines was to screw dist advance up and load car up in gear until audible pinging was heard then back off dist slightly.
That was the most advance a particular engine could handle.
Given the advances in engine materials quality I don't see our engines being any more " fragile" than any previous SBC .
A KS will sense knock ( real or false ) a long time before anything is heard

 

[toptechx6]

toptech
Thank you for the offer of the injectors. I will keep that in mind but first I want to just put a resister on the right bank knock sensor. I was just out looking for the common wire in my case dark blue wire from both knock sensors to the ecm connector. It occurs to me that if I only put a resister on the ks that the electrical connection has turned to dust I will still have one working sensor so the impact of the ecm not being able to retard the spark should not be as bad as if I disable both ks in effect I would have only removed one half of the sensors. I can see why most people would put the resister in the wire close to the ECM because it is so easy to get to but when they do that they do remove all ks protection because that wire is the common wire for both sensors. What are your thoughts on this thinking. I also was thinking that I could have an injector that was intermittent in how it works causing the code 64 Lean 02 sensor on right bank.

I would agree that one knock sensor is better than none, but don't understand why you don't replace the connector. It is available here, see the third row from the bottom.
EFI Connection - TPI Pigtails
The injectors do not need to quit firing to get a lean condition, all it takes is a clogged screen, just because if functions electrically there is no guarantee it will flow fuel.

 

[LLC5]

I will play devils advocate.
While not disputing the reason for the existence of the KS , for those of you old enough to remember; in the good 'ole days, the hot tuning trick for street engines was to screw dist advance up and load car up in gear until audible pinging was heard then back off dist slightly.

I remember it. It was called performance ping.