Knock Sensors

[NYCQDude]

I know OE is always preferred, especially when it comes to sensors. But the OE Knock Sensors are pretty steep $$. Anybody use after-market sensors of decent quality? If not, can someone point me in the direction of the best price point for OE?

Thanks

[Q45tech]

Luckily, Nissan has used the same KS across all models since the fequency response and signal output are shaped inside ecu......as long as the plastic case is not microscopically cracked which changes the internal pressure and thus output significantly.

$300 [2 including new harness] is miniscule compared injectors, CAS, MAF or other sensors.

About the prorated cost of 2 tires which have a much shorter life than the replacement KS.

[NYCQDude]

Thank you Q45Tech. I should change the harness too? The mechanic didn't mention anything about the harness. In fact the car was running fine but a "Service Engine Soon" message popped up on my dash at just under 90,000 miles. The computer diagnostic said 1 KS and Oxygen Sensor. I wanted to change both KS because I know there is labor involved and if one's bad the other should be right behind it. Want to get it out of the way at the same time...

I don't think $300 is steep, but I am also doing some other mods and this popped up right in time to run those off the track a bit lol...

Have seen knock sensors for $25-65 each but aftermarket...I didn't contemplate changing the harness but maybe the same rationale applies to changing both sensors at once?

[Q45tech]

All depends on labor rate and how many decades you wish to keep vehicle.

$400 divided by 13 years is $30 per year from the $2500 annual M&R proration.

What are your future plans when transmission fails? Hopefully you understand.

[NYCQDude]

I do understand. I'll spend the extra duckets and get the OE sensors. I plan on keeping this car a bit longer since a new baby came along and my plans for a Benz CLS55 AMG have stalled = )

transmission's still running strong so far thank God. But I might be making a few mods which could change that. Am swapping the diff to 3.90 or 4.08 (see post: zer...7-q45 ) was planning to rechip the ECU (only found Jet doing it for this year Q, but if you know of others I would love to know about them), will be changing wheels to 18". Will also add a transmission cooler (probably even before modding the ECU).

When the transmission does go I plan of getting a modded JIT or Level 10 transmission because they really are not far off the price of a stock/dealer transmission...

[miata007]

hiI replaced the KS few years ago too at around 130k. Ever since one thing failed after another. Decided to get rid of my 97 at 200k miles. I had to spend $1000/year (for parts only) in the last 4 years of ownership until the car failed smog check. Q is too sophisticated which means more things to break down.

You car still has some life left but keep in mind one day it will be a money pits.

007

[Romeo5k]

okAY all are scaring me. Well, here is my issue at hand. #5 injector went out. I got it replaced with a new one. And now all injectors test between 11.1 - 11.3 So, i have injectors running right. With 226k miles. They missed one of the small lil vaccum hose under manifold, and had to put it back 2 days later.
Now i have a service engine light that comes on after approx 20-30 miles. Sometimes, after 5-7 miles. But anyways, got it tested. And is was a knock sensor thing, saying short circuit or some crap. I dont even wanna think how much this will cost plus labor at 80$/hr

[Unnatural1]

$80/hr...that's a good deal. We get $92/hr.

I didn't think a knock sensor code would actually turn on the engine light. At least, it didn't on my 94 Q. It just set the code but the light remained off. I had a similar situation occur on my Q with the EGR system being the cause of the light.

[Romeo5k]

Im going to get that light scanned again. Because we fixed the EGR problem supposedly. That was a hose issue. But wen scanning, we saw EGR and Knock. But now light goes off and comes on and supposedly its knock.. SO ill go check to it today or something.

[Q45tech]

KS code comes from a resistance check and noise level during cranking, after all KS only remove timing advance and fail safes into a permanent amount during any type of acceleration...............thus weaker acceleration and sometime bucking which feels different from a single cylinder misfire.....depending on wot vs 50%.

[NYCQDude]

A knock sensor fail will turn on the check engine soon light on a '97. That's how I found out mine are bad...

And a word to the wise...if you have to replace a knock sensor replace them both as a pair. You don't want to have to go through this again in a few more months. If one is bad usually the other one is right behind it.

[Unnatural1]

Yep...you're right. OBD II will turn the light on for that code. I missed that we were dealing with a 97 Q. I'm so used to reading about this in regards to the G50 Q's.

[bullittandy]

Thank you Q45Tech. I should change the harness too? The mechanic didn't mention anything about the harness. In fact the car was running fine but a "Service Engine Soon" message popped up on my dash at just under 90,000 miles. The computer diagnostic said 1 KS and Oxygen Sensor. I wanted to change both KS because I know there is labor involved and if one's bad the other should be right behind it. Want to get it out of the way at the same time...

I don't think $300 is steep, but I am also doing some other mods and this popped up right in time to run those off the track a bit lol...

Have seen knock sensors for $25-65 each but aftermarket...I didn't contemplate changing the harness but maybe the same rationale applies to changing both sensors at once?

On 96 and earlier cars it appears that the wiring harness and rubber hoses cook because of higher heat. I have inspected the rubber and hoses on 6+ 97 and later Q45's and the hoses and wiring was extremely soft on all cars. I don't think you need to replace the harness on 97+ cars.

[dlduscg]

I have been getting a P0325, P1447, then just 0325...yesterday I got P0330, P0325, and P1447. All of this started following replacing the crank pulley, idler, a couple of belts, and then finished it off with a fuel induction service. Most of the time I was getting a 1447 purge flow monitor on the evap canister, and only occasionally a knock sensor. The next job I had planned was to replace the battery; the first time I ever had a battery last four years on a Q and figured I'd better be safe than sorry and replace it before I get stuck somewhere. I installed a MTP-24 Interstate battery, erased all warning lights, and so far no problems. I had already ordered to knock sensors and getting myself prepared to do the job, but now I believe the problem may have been the battery. My reasoning is that because the ECU data base does not contain info to diagnose a defective knock sensor per se, and the ECU reacts to fluctuations of knock sensor voltage (2.0 to 3.0 volts), too low or too high a voltage tells the ECU that there is something wrong with the KS, but if the voltage source (battery) is not up to par, then the ECU might generate false warning lights, depending on how critical the voltage variation is. A faulty KS or a faulty hose in the purge flow monitor would not likely heal itself, but installing a new battery would restore the sensor's error threshold to normal....This finding, if correct, means that when checking warning lights, the battery and charging system should always be checked first in order to prevent unnecessary and expensive repairs, and false diagnosis.

[Q45tech]

The computer inside KS system only allows a signal every 90 degrees and for a narrow widow of time before 15 ATDC for each cylinder.

By definition a knock is a preignition before the normal pressure peak at 15 ATDC!
If ignition advance is 20-30 BTDC then the burn speed is ~ 35-45 degrees.

The computer must change the degrees of window to a number of miiliseconds so it knows when and where a knock might occur.

Then if there is a signal in this time period it goes to work.

2 KS [each with a separate listen time gate on off control are needed on a V6 or V8-V12 to avoid confusion time wise.

[dlduscg]

Thanks for the input, however, I was not experiencing a particular symptom of a faulty KS, such as reduced power, indicating that the KS is not doing its job, but reduced battery voltage might tell the ECU that the resistance across the crystal in the KS may have increased, open or shorted, to reveal a defective KS warning light. Thus, a replaced battery can fix the problem, or am I wrong?

[dlduscg]

I guess what I am saying is that a good running Q starts with the best battery you can get. Keep the battery properly maintained and replace it after a reasonable time has elapsed, such as three years old, even if it seems to be fine. Most batteries do not last much longer, even if they are warranted for up to eight years or more. The electrical demand of the Q is high, and if you live in an extreme climate, such as Fl and Northeast, the combined demand takes its toll on the battery and the charging system in general. Engine warning lights are the auto shop's friend, and they are sometimes used to generate revenue. They used to be called idiot lights because they do not really diagnose the problem or give you the information you need to make an intelligent decision for effecting the necessary repair. A fluctuating voltage source such as you might get from a failing battery, can play havoc with warning lights and may cause you to think something is bad and needs to be replaced, when it does not. In my case, it was telling me the KS's were bad, and the evap canister was the problem, when actually it was the battery. The same thing can be said about tires; if you do not drive much, you may think you can probably keep your tires indefinitely, however, rubber and plastic deteriorates in time, and not on how many miles you drive. If you keep your car garaged and do not drive it; in time, you will see the effects of deterioration.