max95q

iTrader: (10)

I know we talk about them going bad. Ive even searched and havent found the cause as to why they fail. So, wht makes them fail? I ask this because i picked up two knock sensors from a local pick and pull. One had a melted connector but looked like it would still work just fine and the other one had cracks in it. is it the cracks that cause them to fail or the connector themselves. I got them for free but the 1 hour I took to get both of them was a pain.

cartman854

iTrader: (2)

The cracks are what cause them to go bad. They can break if dropped during install or hit on something. Any damage on them could be bad. Id just pick one off ebay for $28 and call it a day.

defiance

iTrader: (1)

I would say they fail because of the vibrations of the engine.
Which makes them start to crack up.

trooplewis

iTrader: (1)

First newb I ever saw that had 5,080 posts and Mod status.

bryan163

iTrader: (2)

I've had bad knock sensors with no visible external damage and good ones that look like crap on the outside. The one I'm using right now looks like a rat tried to have sex with it, but it works fine. Knock sensors are actually a piezoelectric microphone. The ECU recognizes knocking by the frequency of vibrations transferred through the engine block.
Microphones are easily damaged by impact or vibration so I would guess that same things can destroy knock sensors. I'd say the vibration probably kills them over time.

sonicrunch

this

and a join date of Aug 2000.

defiance

iTrader: (1)

Hes has got a good question though, why do they often go bad on so many Maximas.

max95q

iTrader: (10)

Its a newb question in the since that I should know this. Plus this is my second 4th gen that I bought in October of last year. The one before never has had this issue thank goodness. Plus Im still new to the 4th gens. For seven years I owned a second gen.

cartman854

iTrader: (2)

Well, if the question is what makes them fail, its the engine knocking, simple as that, or it could be that it was dropped and the internal sensor damaged. So, thats about it.

internetautomar

iTrader: (30)

age, environment, shaking, craptacular design.

trooplewis

iTrader: (1)

And heat soak alternated with cold soak. Worst thing for electronics...

aackshun

iTrader: (3)

This is what I think is the main reason, the KS should be made of something tougher, which would make them more expensive but then again you would probably only need to buy 1 or 2 during a car's lifetime... instead of 4 or 5, I might have to replace mine, but I refuse because I have a 99, and that just makes this daunting task much more fun...

sonicrunch

orly? automotive or altogether.

we could start a turn your computer off vs leave it on debate here.

trooplewis

iTrader: (1)

I was thinking that some smart mechanic would come up with a BETTER place to put the Knock Sensor. I mean, yes...it's in a nice central location now, but wouldn't the concept still be valid if it was on the outside of the cylinder block instead of in the "V"?

I think if octane or timing is off all the cylinders will get some pre-ignition detonation, right? So why not put the KS some place convenient and just let it listen to one cylinder, or one bank?

Maybe the current location is just a "quiet place" except for occasional ping.

trooplewis

iTrader: (1)

Speaking of which (off-topic), I just put a Kill-A-Watt on my power strip that all my computer/monitor/speakers/printer stuff is connected to. Running it 100% of the time, as I've been doing, costs $27 per month. So I'm shutting mine down at night from now on! So are my 2 kids with both their computers...

sonicrunch

mechanic?
mechanics are idiots. You mean engineer. a different kind of idiot.

sonicrunch

really? wow. that is a hell of a lot more than I expect. My whole house is only 50 bucks a month.

internetautomar

iTrader: (30)

the reason for putting it in the V is so that it can read all the cylinders with 1 sensor.
There is a better designed sensor out there, it was used on the VG in the 3rd gen, GM used it on the TPI motors too. It is all metal and looks like an oil pressure switch. I get the feeling that it is not as sensitive as these plastic ones though. Both aforementioned examples also had the KS on the side of the block rather than in the V

cashoit

Yeah...i have seen them on the side of the block as well. But in all honesty..inside the "V" ( what a technical term lol) is the best place to locate the knock sensor. the sensor should be as symmetrical as possible with all cylinders and where it is located is a beautiful position. Its not so convenient for us tho but its a good location for the engine.

I think it cracks cuz the bolt is originally overt-torqued. And combined with the natural vibration of the engine under hard throttle, it jus over stresses the KS. And the material its made of is unsuitable for those conditions.

madd_maxx

iTrader: (1)

I'm on my third knock sensor, all were oem Nissan non had any visible damage.

Godzillamax

Uh, 'ya think it might have anything to do with the fact that it's rubber, and stuck under the UIM surrounded by scorching hot iron on 3 sides with no ventilation for thousands of hours?

cashoit

yeah that could contribute a lil too lol

internetautomar

iTrader: (30)

it's plastic not rubber

max95q

iTrader: (10)

So, it turned out to be more than the knock sensor. It turned out somehow someone jimmy rigged the pig tail to the knock sensor. The negative wire was cut and fraid inside the pig tail harness. So there wasnt a connector going to it at all. So i had to make a new negative wire from some wire I had in my closet from my stereo which turned out to be the same thickness. I then had to make my own connector to fit inside the plug that connected the knock sensor to the pigtail. I did this by molding/bending a connector from my stereo to fit inside the plug and fit the size of the knock sensors connector. This all took about 2 hours to do. After that I secured the connector inside the plug and used electrical tape to tape everything back up and used the junkyard knock sensor. I kept my original one just in case. Great news, no more knock sensor code. Some how this not only cleared up the code but I remember someone talking about how it fixed his starting problems with his car. My car had a cold start issue only when it was cold outside, that is also gone. Dont know how but it is. While doing this I remembered how fun it was to work on a car.

internetautomar

iTrader: (30)

the knock sensor only uses 1 wire on the harness.
the sensor side of the harness is only 1 wire from the factory.

defiance

iTrader: (1)

Which is why its so easy to splice and replace with another wire.

max95q

iTrader: (10)

Then why did the maxima's i pulled the knock sensors from have a positive and a negative wire going to the knock sensor. Mine had one wire though. Im going to have to check my 95 then. Thats what made me connect the other side in after seeing the cut/fraid black wire inside.

cashoit

cant argue with results brotha...if it aint broke dont fix it lol

internetautomar

iTrader: (30)

I bought the sub harness from the dealer, the harness side has 2 wires, the KS side is 1 wire.
Mine is a 95

max95q

iTrader: (10)

thats probably what ive been seeing then. Its been raining and cold so I havent had a chance to see anything different. So in the end it seems me just changing my knock sensor did the trick. Cant say it wasnt fun.