Homemade Knock Sensor

[DanAatTheCape]

While traveling out west last summer I overheated - badly.   Afterwards I got the dreaded code 52 (knock Sensor)

 

When the ECU does not "see" a KS, it puts the vehicle into limp mode.

Usually the code 52 is related to the knock sensor wire harness.  To change either requires removing the intake manifold which means taking off the top of the engine.  

Since I was on the road I did not want to get into such a massive job if I could avoid it.  After some internet googling I made a KS which I bolted to the rear engine hook (for removing engine).  I had several iterations - first gluing to the hook one piezo, then 2 . The lower one would melt (too close to exhaust manifold).  Eventually I took 3 (in series) and glued them to a small piece of metal & bolted onto hook.  (JB weld=glue)

These piezo transducers (AKA "buzzers") generate a small amount of electricity when vibrated.  A KS is a piezo transducer.  The ECU advances the timing until the KS starts reporting too much vibration (knocking) and then the ECU backs off a little.

The KS harness connects to the harness on the drivers side rocker arm cover (fuel injectors). I was able to move the throttle body and get to connector underneath.

I got the piezo transducers at radio shacks.  I went thru 5 of them before I got something what worked fairly well - $1.99 at Radio Shacks and got one off ebay $4 or $5. I did get a code a few times on the way home. I would pull the negative terminal off the battery and clear the code. 

 

 

 

 

 

 

 

 

 

[zero]

I've got a diesel timing light adapter that uses a Piezo transducer that converts when it "hears" and injection pulse and turns it into an electrical signal.  I had never given it much thought before you mentioned it as it applies to the knock sensor on the Toyota. I always assumed the knock sensor on my 1988 22RE didn't do a thing, but maybe I'm wrong?  When I had the head off and milled it a little,  it was just enough to make the engine knock unless I used high-test instead of regular. I finally just loosened the distributor and turned it until I could use regulator without pinging/knocking.  If that knock sensor on mine does anything, seems it is not much.

[Maineah]

Why not just buy the sensor and fasten it to the block? It does not have to be under the manifold all though it probably is the best place for it for accuracy.

 

[DanAatTheCape]

<<<< Why not just buy the sensor and fasten it to the block? >>>>

 

the real toyota sensor cost $150 bucks (that is the discounted price).  as you noted, where it sits in the bottom of the "V" both banks are equally distanced.  I was hoping not to have to buy a KS. When I got in there it looked so bad, and given the effort to get in there, I changed it while I was in there.

 

When I was researching, some had mounted it externally by welding a nut on the hook and screwing the KS into it. 

 

What I made did not require any welding.  Knowing what I know now (hindsight is 20/20) I would have tried the external KS with the welded nut for mounting.

When I flipped the top part of the  intake, I discovered the wires to the #6 fuel injector was damaged.  Looks like a mouse ate the wire.  I had pulled a nest out from there in the past.

I also found that the exhaust valves badly needed to be re-gaped. (older post) 

 

Edited May 8, 2016 by DanAatTheCape

[DanAatTheCape]

3 hours ago, jdemaris said:

I've got a diesel timing light adapter that uses a Piezo transducer that converts when it "hears" and injection pulse and turns it into an electrical signal.  I had never given it much thought before you mentioned it as it applies to the knock sensor on the Toyota. I always assumed the knock sensor on my 1988 22RE didn't do a thing, but maybe I'm wrong?  When I had the head off and milled it a little,  it was just enough to make the engine knock unless I used high-test instead of regular. I finally just loosened the distributor and turned it until I could use regulator without pinging/knocking.  If that knock sensor on mine does anything, seems it is not much.

I would be surprised to be able to evaluate a KS with the engine at idle or not at load.  As for timing by moving the distributor, that usually works. Never looked at the 4 cylinder, but on 6 the proper method is to put a jumper on 2 of the connections (same set that makes the check engine light flash so you can read codes) and then set it at 10BTDC. When the jumper comes out it drops to about 8.  I have heard that many set it around 11 or so for better performance.

As I understand the ECU logic, under a load as the ECU is comparing mass air flow to oxygen sensor reports, it is advancing timing until the KS voltage increases and then backs off on the timing.  

I have heard of milled heads increasing compression, but not for small amounts.  Would be curious to see how close you are to timing spec.

 

It is possible to test a KS.  If you measure voltage at the KS you should see some very small voltage with engine running.  I have read of a test where one takes an air impact hammer and  taps the block nearby with the engine off to see of the KS makes voltage output.  If your ECU is not flagging the KS I would bet it is working.

 

[zero]

Is your engine a V6?  I ask because I noticed whenever Toyota does a warranty head-gasket replacement on the 3 liter V6, they put in a new knock sensor as part of the warranty. I find that odd unless they had problems with them particular to V6 engines.

[DanAatTheCape]

yes V6, I thought I tagged VZ3E.    The head gasket recalls were done a long time ago.   I think it is SOP on this engine to replace the KS wiring harness whenever they go in there.  The harnesses cost less than $20 and are the weak link    (I am told)

[Jaunt]

yeah always replace the harness when doing the sensors, cheap insurance.