Does anybody know what the Knock Sensor looks like?

[pabs324]

I have searched on the forum and cant find. I looked for the part many websites and i keep getting two knock sensors and keep getting two different looking sensors. are they both compatible.

[Q45dude]

There are two knock sensors, both look the same. here is a pic.

[Kiven422]

Where are they located in the car?

[qship96]

There are sooooo many threads with pictures and instructions about knock sensors on this board, use the search function and read them! Sorry to sound mean, but do your homework!

[maxnix]

1.) I have searched on the forum and cant find.

2.) I looked for the part many websites and i keep getting two knock sensors and keep getting two different looking sensors.

1.) You may need to review the search tutorial sticky in the Infiniti Q45 Forum.

2.) For the engine and intake and exhaust, there are only two sites you really need to know.

http://www.infinitipartsusa.com

http://www.sparkplugs.com

[pabs324]

thanks q45dude. thanks for the help guys. I can get two of those knock sensors for 90 brand new

[greg100]

Where did you find both knock sensors for 90 bucks? Minimum is 100+ on ebay.

[pabs324]

on Ebay someone was selling them for 49. he only has one left

[James_75]

I've searched some sites and I found out that knock sensor is considered as the heart of car's engine. It primarily functions to manage the way your car burns fuel, to ensure that lesser gas is wasted. In its most basic sense, knock sensor picks up the vibrations that come from engine fuel combustion. It is a miniature microphone that can be seen mounted on the engine block. Its location may vary depending upon the configurations of your car.
Modified by James_75 at 4:50 PM 2/27/2008

[bombs]

A knock sensor is device mounted on the engine that is designed to detect the high-frequency vibrations caused by detonation.

[Q451990]

I've searched some sites and I found out that knock sensor is considered as the heart of car's engine. It primarily functions to manage the way your car burns fuel, to ensure that lesser gas is wasted.

Interesting first post...

I would compare it more to the ears than the heart. As bombs said they are essentially little microphones that listen for detonation, more commonly known as "spark knock"

When knock is detected the ECU retards the timing advance to help eliminate the knock. On the Q45, the ECU also checks to make sure the sensor are functioning... so if the KS fails, it just sets the ECU into full protection mode - as if it's making the assumption that the spark knock is there all the time.

Bottom line is less power and sometimes strange driveability issues like occasional bucking, etc... Most people say "something just doesn't feel right, but I can't put my finger on an exact symptom"

Heath

[Haitian_King]

Hmm. Good to know. It might be time for me to change mine. 91.3k?

[Q45tech]

Actually the KS circuitry advances the ignition until it hears knock then starts a progressive back off in steps until the knock stops. It knows that it is harder to stop knock once it starts than to never allow it to begin in the first place. So it remembers the advance that seems to work...........but periodically tries to add advance as long as rpm are constant [highway cruise]. I believe the knock flag is tested evry 2-5 seconds depending on rpm.

Under low load cruise conditions the higher the advance the more fuel efficient the engine is!

Turning on/off ac set a knock flag so the cycle can be adjusted to optimize situation.

In theory the KS system can run different advance for different banks [why 2 sensors] but unless there are significant differences [bad injector/plug] both banks should be equal BUT there is always a WORST cylinder that starts to knock before the others.

KS SYSTEM is there to squeeze the last MPG out of situation.

Remember the KS system stops being looked at when rpms exceed 4500 rpm, so it is not really for WOT where advance is looked up in the PROM [it can still work partially but not as well as at 2000-3000 rpm.

The following explains how the KS IC decides and creates a signal to ecu:http://www.intersil.com/data/an/an9770. ... ic8101.pdf

Don't confuse cruise and sudden tipin knock with WOT knock!

[Haitian_King]

Uh, sure.

But uh, when's the "right" time to change them? Their estimated lifespan is?

[Q45tech]

Depends on ambient temperature and mild-severe overheats as there is not much safety in the plastic between normal summer after run shut down under plenum peak temp and the cracking point temperature.

The maximum operating temperature is 250F per spec sheets and 10 minutes after shut down the temp reaches/exceeds this if 100F outside.

Historically without a overheat [from defects] the KS last at least 7 years and 100k.

Mine lasted 10.5 years and 205,000 miles, most seem to fail around 10 years in ATL metro.................other locations will vary.

We have changed over 100 set of sensors and harnesses since 1997.

I already have my spares sitting awaiting the expiration of 10 year life of set #2 should be about 2010-2011.

One is constantly looking at ebay and others for that special deal on common parts.

But then again you must be sure you will have the specific vehicle for years to come.

My next car will be all electric or steam/nuclear waste with radiation focused rearward.

[maxnix]

With no reverse, I presume.

Reminds me of Stanley steamers (great, if you are not in a hurry and can wait for it to reach temperature), or the futuristic Ford pwered by a fission reactor at teh Seattle's World Fair. Would have weighed 10 tons with all that shielding.

[pabs324]

where can i get a KS harness and is it required when changing the KS'?

[[email protected]]

Actually the KS circuitry advances the ignition until it hears knock then starts a progressive back off in steps until the knock stops. It knows that it is harder to stop knock once it starts than to never allow it to begin in the first place. So it remembers the advance that seems to work...........but periodically tries to add advance as long as rpm are constant [highway cruise]. I believe the knock flag is tested evry 2-5 seconds depending on rpm.

Under low load cruise conditions the higher the advance the more fuel efficient the engine is!

Turning on/off ac set a knock flag so the cycle can be adjusted to optimize situation.

In theory the KS system can run different advance for different banks [why 2 sensors] but unless there are significant differences [bad injector/plug] both banks should be equal BUT there is always a WORST cylinder that starts to knock before the others.

KS SYSTEM is there to squeeze the last MPG out of situation.

Remember the KS system stops being looked at when rpms exceed 4500 rpm, so it is not really for WOT where advance is looked up in the PROM [it can still work partially but not as well as at 2000-3000 rpm.

The following explains how the KS IC decides and creates a signal to ecu:http://www.intersil.com/data/an/an9770. ... ic8101.pdf

Don't confuse cruise and sudden tipin knock with WOT knock!

Hi Q45 Tech,

Once the knock sensors have been replaced, how many miles do you have to put on the car before the computer resets itself to recognize it for emissions purposes? I have a 96Q.

Thx,Bobby

[Q45tech]

It is not just miles but crank and warm cycles with miles so don't just drive 100 miles on highway and expect it will be ready for testing. Do 5 - 15/20 mile cycles with a cold to hot warm up each time.

You should reset the stored code with a scan tool immediately and make sure it doesn't come back [that you replaced KS correctly].

All wonderfully and fully explained in your FSM.

[maxnix]

where can i get a KS harness and is it required when changing the KS'?

Yes.

http://www.infinitipartsusa.com

Also get KS there are at

http://www.sprakplugs.com

but call to verify you get the right ones. All else are factory rejects or worse.