anyone expirienced a bad knock sensor?

[supraduper]

i need some help.

i am wondering if anyone has ever expirienced a failed/failing knock sensor on a 7MGE? what are your symptoms?

anyone know how to definitively diagnose a knock sensor?? (nothing in the tsrm)

i have this problem where the engine kinda boggs down in mid to upper RPM..

-its not the ACIS, verified and properly functioning..
-VAF checked with lab scope, ok
-TPS checked with lab scope, ok
-plugs wire cap and rotor new, oem plugs oem cap and rotor
-intake air temp and coolant temp sensor both checked with multimeter, ok

i believe the knock sensor is at fault, or the connection at the sensor is loose..
no check engine light on
no codes


from what i read, the only time a code would be set is if there was an open in the circuit..


so i ask, has anyone with a 7MGE, had a failing knock sensor and can enlighten me on:
A. a way to diagnose it..
B. symptoms? how the engine will drive with a bad knock signal?

thanks in advance

 

[Nick M]

You can definetively diagnose by checking with a scope at the sensor itself. You can just tap on the block. If you are good, then recheck that same signal at the ECU. No signal, bad wiring.

 

[supraduper]

isnt there a connector in the diag box that is for the knock sensor?

 

[jetjock]

No. And stop messing with the knock sensor. It has nothing to do with your problem.

 

[Max Vador]

knock sensors make their own signal so you can ground and hook up a multimeter to the one wire coming off of it and just tap the block near the sensor and you'll see it works

 

[supraduper]

jetjock, if you have some useful input to add then share it.. otherwise shut up. i hate people like you... you didnt even read my post, who said i messed with the knock sensor, i was merely inquiring about it..

i know the timing is retarded (like jet) when the knock sensor is no good... and thats what i am feeling... a lack of timing advance in the upper rpm's... thats what it feels like at least... it doesnt pull like it used to..

 

[gennro]

jetjock, if you have some useful input to add then share it.. otherwise shut up. i hate people like you... you didnt even read my post, who said i messed with the knock sensor, i was merely inquiring about it..

i know the timing is retarded (like jet) when the knock sensor is no good... and thats what i am feeling... a lack of timing advance in the upper rpm's... thats what it feels like at least... it doesnt pull like it used to..

Hey man calm down he is just telling you the knock sensor has nothing to do with your issue. If you have a bad sensor you will have a check engine code. A knock sensor generates a alternating current depending on the vibrations that is applied to it. Just get ready to get schooled though.

Here some links to start with

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=IG&P=1
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=1
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=EM&P=5

Codes 52 or 53 would be what you are looking for
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=23
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=28


Also what you are experiencing could be old spark plugs, wires, worn out distributor cap, bad gas, clogged air filter, old coil,clogged fuel filter, vacuum leaks, incorrect base timing, worn out engine, etc etc etc

 

[ben1984j]

jetjock, if you have some useful input to add then share it.. otherwise shut up. i hate people like you... you didnt even read my post, who said i messed with the knock sensor, i was merely inquiring about it..

i know the timing is retarded (like jet) when the knock sensor is no good... and thats what i am feeling... a lack of timing advance in the upper rpm's... thats what it feels like at least... it doesnt pull like it used to..

His input was plenty useful...it is true that a faulty knock sensor will not cause your problem. I think "messing with it" in this context means "attempting to diagnose it and looking to it as a possible cause of the problem"...

The knock sensor contains a piezoelectric element that produces a voltage when subjected to vibration. Besides knock, there are other kinds of vibration that occur in the engine (ex. ignition), so the sensor is calibrated to produce maximum voltage at the specific frequency where knock occurs (about 7 kHz if I remember right). The ECU only pulls timing when KS voltage goes above a certain threshold.

This system can't fail in a way such that timing will be pulled continuously, except under circumstances that will set a code 52...if there is an open in the KS circuit, the ECU goes into fail safe mode and sets a fixed timing retard angle. Which will cause symptoms similar to what you describe, but since you don't have a code 52, as others have said I would be looking elsewhere for the issue...

 

[jetjock]

jetjock, if you have some useful input to add then share it.. otherwise shut up. i hate people like you... you didnt even read my post...

I read your post moron, that's how I know your KS isn't involved. And hate away. I'm not here to make friends. Frankly I'm not all that impressed with lazy dimwits who're unwilling/unable to even read a schematic of the diag box. Guess that makes us even. The only difference is I won't be needing your help in the future...

 

[supraduper]

now i can see his post being usefull if he provided me with some of the useful information that was provided to me by, gennro and ben1984j... that is useful information, just saying that isnt my problem doesnt help me, as that sounds to me like its only your uneducated opinion.. which seems to be rampant on any forum you see...

in response to "Frankly I'm not all that impressed with lazy dimwits who're unwilling/unable to even read a schematic of the diag box.".. i have done plenty of research using the search and have used the tsrm to look at schematics... but i didnt specifically look at the diag box schematic.. i thought someone would have been there and done that, who was also willing to help with some information.... and the basis for me asking that question is that i remember seeing a connector labeled Nox, thought it might be the knock sensor...

in response to gennro, i have replaced the plugs, wires, cap and rotor all with toyota parts.. air filter is clean, coil has been replaced to no avail... no vacuum leaks, intake smoke tested, all vacuum lines routed correctly, engine rebuilt within 7k miles. done to spec, no knocks, noises, oil consumption, compression 150 across the board... base timing is set to spec.. the only thing i havent done is the fuel filter, car has 140k on it... and the problem isnt consistant with a clogged filter, as far as the problem isnt the same everytime, sometimes it pulls ok sometimes not at all

my thought is there is a loose or shitty connection at the knock sensor connector causing the resistance values read to be incorrect... as if there was a loose connection it may not read open, but it could increase the resistance, causing the computer to read a knock, hence retarding the timing..

thanks to all who help, i am not an uninformed driver looking for the generic answer... i am a tech and i have looked very far into this and have tested numerous sensors and came up short on information on the knock sensor... all i need is information to fix my problem...

i was hoping someone could provide me with a frequency value of a normal good running engine so i could reference it to mine... and i thought there may be a better place to access that signal other than tapping into a shielded wire.. the tsrm has nothing on knock sensors and all i can find in the search is the rewire, and schematics dont give you specs, just how everything connects to each other..

 

[jetjock]

There is no connector labeled Nox. The signal can be checked at the ECU, which would be the correct place. A competent tech would already know this.

My "uneducated opinion" has been offered here five years, some of it as the first and thus far only electrical and ecu subject matter expert. I could easily answer your questions in detail. Hell, I could have answered your first question about checking the knock sensor but didn't because 1) It has nothing to do with your problem and 2) I saw a guy with a lab scope asking how to test a knock sensor. Nuff said.

But the real question is why you don't perceive value in being told you're wasting time looking in the wrong place. Not to mention your posts demonstrate a lack of understanding about how the knock control and diagnostic systems operate and the proper way to use factory and online service documentation. Put simply you *are* an uninformed owner and all things considered your claim of being a tech isn't exactly something I'd be boasting about...

 

[Dirgle]

The output of a knock sensor is not frequency, you're looking for voltage. By design a KS will generate a voltage spike on it's output, when it is vibrated at it's tuned frequency. And due to simple electromagnetic properties a KS will produce no voltage if it fails. It is impossible for a once functioning KS to go bad and still produce a voltage.

The plain and simple is that a bad KS will never retard timing, even if the engine experiences knock. Sorry, JJ was right in telling you to look elsewhere before investing to much time down this path.


Here is a brief explanation of the Toyota KS in PDF.
http://www.google.com/url?sa=t&sour...LIvGxkLqYBC3XU7pg&sig2=1dMEjMvys_7q-NxTdrKahQ

 

[supraduper]

again. this post is not necessary it has nothing to do with my original post, you are now just asserting your presumed authority of king dickweed. if you dont have anything to say on the topic then go away. you obviously dont have any knowledge worthwhile to me, if you do then keep it to yourself, there are many other more helpful and less flame throwing people out there.

and obviously you can test it at the ECU! if you have a sensor, it connects to the ecu? is that what your saying??? no shit retard
if you can easily test under the hood, why not? if you have a good value then procede to the ecu... and look for a discrepency.. correct?
sure you COULD start at the ecu.. but if there were another spot which didnt require removal of other peices, why not?

at this point i think the mods should delete both our last posts and let this thread continue on to its desired course...


and if someone tells me that im going in the wrong direction and can provide me reason i will be more than happy to concede to the facts. but if all u say is that i'm wrong, stop fucking with it.. then im not going to perceive that you are educated and will presume you are just a flaming tool bag. how is just saying im wrong helpful? in anyway? am i suppose to believe you? take your word? dont post a reply unless you have facts... and if you have facts share them.


and finally, NO SHIT i dont understand the knock control system or i wouldnt fucken be here now would i? any competent human with common sense would realize this.

thanks, mods please clean this tread up so its useful to people.

 

[Dirgle]

and if someone tells me that im going in the wrong direction and can provide me reason i will be more than happy to concede to the facts. but if all u say is that i'm wrong, stop fucking with it.. then im not going to perceive that you are educated and will presume you are just a flaming tool bag. how is just saying im wrong helpful? in anyway? am i suppose to believe you? take your word? dont post a reply unless you have facts... and if you have facts share them.

Did you even read my post, or are you so heated right now that you're not thinking rationally?

 

[supraduper]

thanks dirgle... so if the engine isnt knocking there is no signal sent to the ecu?

i didnt think my KS was bad, but i had a bad connection...

---------- Post added at 01:45 AM ---------- Previous post was at 01:43 AM ----------

i just think that if your going to take the effort to say something, please back it up.. im here to learn, and i wont learn if people just say "no, thats not it" ........why? why?

---------- Post added at 01:46 AM ---------- Previous post was at 01:45 AM ----------

Did you even read my post, or are you so heated right now that you're not thinking rationally?

yes i read it after my message posted

 

[Dirgle]

Sort of, the KS will produce less voltage, especially at multiples of it's tuned frequency. But the voltage will peak at it's tuned frequency. The ECU is looking for the voltage to reach a certain level. When it does, it knows that the KS has encountered that frequency and retards timing accordingly.

A bad connection will generally throw a code 52 in the ECU, and since you said you have no codes I doubt this is the issue. The issues you are experiencing are not the result of faults in the knock sensor circuit.

 

[gennro]

A bad connection will generally throw a code 52 in the ECU, and since you said you have no codes I doubt this is the issue. The issues you are experiencing are not the result of faults in the knock sensor circuit.

Knock sensors only do one thing and one thing only and they either work or don't. If they don't work then the TCCS will output a code. You have issues in another place. I would be checking your ignition system and replacing that fuel filter.

 

[IJ.]

And this is done, twice people have tried to help you and you've thrown a hissy fit like a little girl....

Here's an idea if you're not willing to listen to advice when people try to help you go elsewhere to ask your questions.