Knock - Is It Real or False? Save Your Engine from Detonation!

How can you tell if the knock you are seeing on your scanner is real or false? Watch this video as The Tuning School's Bob Morreale describes 3 key steps to determining if the knock is real or false. Don't be like all the bad tuners out there who simply "turn off" the knock sensors - it could destroy your engine! Instead, learn how to properly and safely tune!
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[@jd4evr2001]

Raising OCTANE to highest level SOLVED my persistent problem on 2010 Chev EQUINOX. The high ethanol levels in gas now is bad, especially. No mechanic was able to diagnose the meaning of the knock sensors' alarm for months ! A truck driver/mechanic gave me the same advice as yours& my SUV is back to normal. No more bad habits on letting the gas tank go low either.

[@TheTuningSchool]

Very good point on the gas tank. We're happy to hear your problem is solved. Feel free to reach out to us with more on your tuning journey!

[@jd4evr2001]

@Buzz Lightyear Sorry I missed your comment when made: you will also get perhaps 20% more mileage with the highest octane levels hands down.

[@Blacktopmafia660]

Great advice. Exact same procedure I follow. Side note..i always end up desensitizing hemi knock sensors. The factory has them set pretty high.

[@TheTuningSchool]

Awesome! Thanks for watching

[@arielatom03]

Dont forget coolant temps and intake temps play a huge role in knock, i know they are not easy to improve but super important when it comes to knock.

[@ForzaRT]

Very nice info... Sometimes the knocking is produce for cooling system problems.

[@chrissnyder6787]

Thanks.. Good info. I disconnected 93 GMC 1500 4.3L V6 knock sensor a couple years ago (and backed off the timing) when I got the truck, as I thought occasional scanner knock counts were bad (from sheet metal rattling on engine or ???) since they happened while idling/revving up a bit in driveway. But now think it's not so unusual and the computer might sort these out. I know what detonation can do so don't want to take a chance, but it's time to tune this engine right, as I'll be driving it more this winter.

[@KHIJAPAN]

Very good advice

[@donalic]

This is gold video!!!!!!

[@glennmassengill3532]

Good Pro Tip on knock! Takes a few extra steps, but worth the effort for sure. HP isn’t cheap why change blowing your motor over half ass tuning...

[@willyck948]

I participate in garden tractor pulls and would love to be able to tell if fixed timing is correct wile tuning. Been looking around for a way to add and monitor knock sensor

[@ginoasci]

A MYSTERY !!! New motorcycle runs GREAT on 87 octane and Castrol 10W-40 synthetic oil. 600 mile service, still runs GREAT on 87 octane and Castrol 10W-40 synthetic oil. 1806 miles, 87 octane and Castrol 10W-40 synthetic oil. ENGINE KNOCKS. This time a Full tank of 93 octane and Castrol 10W-40 synthetic oil. STILL KNOCKS. This is on a Triumph bonneville 1200 engine. Seems to be a common occurrence on these all over the world. So it can’t be the gas or oil obviously. England had very high octane fuel but they still knock. We were thinking the cam-chain tensioner but the oil is always the same. High octane fuel doesn’t eliminate the knocking. Tried that myself just yesterday. The only thing I can come up with is a software problem with the ECU during the service at the dealership. Considering this is the common denominator because the bikes are serviced at different dealers in different countries BUT connected to the same mainframe in London to Triumph headquarters that effect the bikes that get ECU updates. From the information given in this video if the timing is off, or the mixture and the timing is off, the result is a misfire. What else could it be ????? Triumph tells us it’s normal but my these bikes run GREAT other than this knocking. People have tried valve adjustments, with no difference. Keep in mind these are NEW motorcycles. Help please ……..

[@MerciaAnglii]

An interesting video, although the part that is wrong in the video is where the person describes the detonation noise as something being produced by “the piston literally rattles & fights its way up or down in the bore…” If there is enough/excessive clearance between the piston & bore for the piston to rattle during detonation, then the engine has bigger issues than just detonation. The sound of detonation is actually created by a small part of the fuel/air mixture combusting at supersonic speed (uncontrolled combustion). This creates a supersonic shockwave that creates a supersonic sound. That sound is generally known as pinging; pinking; combustion knock, and or detonation. Detonation is where the speed of combustion in the chamber can reach speeds of mach4. (over 3000 mph) Normal (or controlled combustion) occurs at subsonic speeds. Where the “flame front” travels across the combustion chamber at speeds usually between 35 to 120 mph. Otherwise known as “Deflagration”. In order for detonation to occur, deflagration (normal combustion) would have had to start first. I think the person in this video is also getting a little confused with pre-ignition & detonation.

[@BobRocket78]

Thanks for the input! We have seen the issues described in the video during normal operations. It's also not uncommon for us to hear the LS Engines rattle on cold start for the same reason (Piston rattling in the bore on the wristpin axis, excessive piston clearance before the metals grow), called piston slap - on normal healthy LS Engines.

[@MerciaAnglii]

Thank you for the unexpected reply - and from the man himself! I’ve watched a number of videos from this channel, & learned a lot. It’s just that some parts of this video seemed a little confusing to me. I’m not familiar with the LS engine that you mention in your reply, but as well as the excessive piston to cylinder clearance that you mention, maybe the LS engine also doesn’t have enough offset of the wristpin centre line to the piston centre line in its design. If it had sufficient offset, then perhaps it would have less or no piston slap? The main point of your video is to point out why people shouldn’t turn off their knock sensors. I too don’t understand what possesses people to do that. It seems like an unnecessary way of slowly destroying an engine - that is, if the knocking/detonation is bad enough. The localised heat of detonation eventually causing holes to melt into piston, & the shockwave of detonation eventually causing cracks to appear in pistons, valves, & head. It’s my understanding that detonation is predominantly a post-ignition issue. The expanding burning mixture of “normal combustion” compressing parts of the as yet unburnt mixture, causing the unburnt mixture to suddenly & significantly rise in temperature the spontaneously detonate. (As the Flame Front of normal combustion travels across the chamber, it compresses the as yet unburnt portion of the mixture). Pre-ignition can contribute to the post-ignition of detonation, but they are two separate events. As you mention, other contributing factor of detonation are higher cylinder pressures & temperatures prior to the spark-ignition event and after it. Perhaps caused by too weak a mixture; a spark that is too far advanced; compression ratio too high, and even an engine that is generally running too hot. Engine builders sometimes forget about the extra cooling that might be necessary.

[@BobRocket78]

I'm always happy to talk, thanks for watching and commenting!

[@romeovicentini6643]

Speaking of Pre-ignition and detonation, is detonation occurs always after the normal combustion initiated from the spark? In the video it confuses with Pre-ignition isn't it?

[@romeovicentini6643]

Also, I have an another question, if you have a false knock, do you de sensitize the oem or the extra aftermarket knock sensor that you have installed for the tuning process? cheers mate

[@kolemieux]

Exceptional as always Bob

[@TheTuningSchool]

On behalf of Bob, we thank you for watching and subscribing!

[@exploringgodscountry]

At 3:43, I assume you mean unless you get off throttle or add more fuel? I'm tuning PE and I notice when I'm not in PE mode, knock may start, but as soon as throttle hits setpoint and PE turns on, then the knock reduces / goes away.

[@charlieryan1736]

Thanks for making this informative video

[@TheTuningSchool]

Thank you for watching!

[@dalelockett2619]

FYI........... On Ford Spanish Oaks PCM calibrations, I've discovered that the Ford engineers made a KS mic to cyl assignment mistake that was throwing the engine firing order cyl noise phase sequencing out of pattern causing some potential false knock when using the OEM Ford per cyl sensitivity threshold map settings untouched. They assigned #7 cyl & #2 cyl, #6 cyl & #5 cyl to use the same KS mic in a 90* firing sequence pattern that the other cyls do not experience which throws the firing cyl noise phase sequencing off. The fix is to reassign #2 cyl from #0KS mic to #1KS mic then reassign #6 cyl from #1KS mic to #0KS mic.........now ALL following cyls will be using the opposite KS mic from all leading cyls in the 90* firing sequence according to engine firing order now, which cleans up the cyl noise profile when the cyls are fired thus PCM can now more accurately decipher any out of firing pattern cyl noise spiking as white noise against any in pattern firing cyl noise that spikes above the normal pattern thresholds as actual cyl knock. This reassignment showed to resolve all the reported issues w\ Per Cyl Mode knock detection & will improve Global Mode knock detection since this assignment mistake is negatively affecting both modes. Just trace the current cyl to KS mic assignment in tune file according to engine firing order sequence & you'll see that #2 cyl & #6 cyl are out of sequence......................

[@thisisyourcaptainspeaking2259]

Fantastic observation, I'm impressed!

[@jamesavery6671]

Thank you very much. I think I am getting false knock in PE mode. Engine is a stock LM7 9.5 compression running 89 octane. I'll richen up PE to see if it makes a difference or pull timing. Commanded PE is 12.45 afr with timing at 25 degree's WOT. Too lean of a PE ratio ???????? To much timing ?????? Not enough octane ?????

[@TheTuningSchool]

Hey James, try changing each part of the problem individually, run a slightly richer AFR, then run slightly less timing, then try adding some octane. After each condition change check to see if the knock changes. These tests are all assuming the knock is fairly consistent. If it intermittent, it's more likely to be false and it will be difficult to accurately test. The one thing I will say is that I think you are testing the limits of 89 octane with such high timing and lean AFR.

[@weldtestservicesllc633]

Excellent video. Thanks for sharing!

[@TheTuningSchool]

Thanks for watching!

[@dr.brianadams6542]

Just bought a vehicle the was tuned by the previous owner. Poking around the tuning file, I see he desensitized individual cylinders at certain rpms, am I safe to turn those all back to 0 and then run some logs?

[@TestAndTune]

What's the difference between negative knock and positive knock?

[@whatluck1508]

I have a 2007 pontiac grand prix with the 3.8l V6. I got a ZZP tune for it, and from what i can see it pulls timing up to 6 degrees around the RPM range of 4k - 4.4k RPMs So far i have tried lowering the AFR from the 14.7(ZZP tune) to 14.3(factory), and noticed that it reduced it, so far i have it at 13.9 AFR and got it to where it is now. Before it would go to the max of 8(they changed it from 15 to 8) degrees on the ZZP tune, havent tried factory. But does this sound more like a tune related problem or if it could actually be mechanical problems. I am not hearing any abnormal engine noise.

[@adamliebler7610]

Super helpful video. Thank you!

[@TheTuningSchool]

You're welcome. If you haven't already, subscribe for more updates!

[@dummkompf]

How bad is it to repair the end of a knock sensor wire? I know it's best to replace because of the shielding, but the part I'm repairing is just the last few inches of wire. The part that was damaged wasn't even inside the shielding to begin with, but I did have to cut the shielding back by a couple inches in order to get some good wire to splice to.

[@Fa5_4_lyfe]

Enjoyed the video guys thank you

[@TheTuningSchool]

Glad you enjoyed it! Thanks for watching!

[@lifeishard1211]

Bob mentions desensitizing the knock sensor once all the steps have been followed and it's verified to be false knock. is there a guide on doing this safely, for example 5% at a time like he says?

[@TheTuningSchool]

Yes, increase the knock sensitivity 5% to 10% at a time is the process we recommend.

[@Recipro1]

Want to relocate ks on a f150 5.0l fi. 1. Book says original is a 65khz two wire sensor 2.how are wires connected to sensor via signal return and v.reference . Seems like green wire to power and black wire to ground . Any good info?

[@thedobermangang3503]

hey got a question for you i got 1990 blazer 5.7 tbi had engine rebuild about month ago got a few up grades bigger cam so i had to get my computer chip tune to raise fuel and timing on the chip i change pressure regulator and adjust that the cam i have in there is xe 262 h comp cam the block was 30 over.and i still have the factory swirl port heads i should had put some vortec heads on there...but for some reason cant get it to run right just dont have no power and im getting a ping sound from engine and #6 had oil on spark plug threads only the rest of plugs are fine i dont no where im getting the ping sound dont no if the oil on the spark plug have anything to do with it or something with the fuel and timing is not right..

[@nawarbakree5005]

Hello... I have a car type Kia 4-cylinder engine size 2400 GDI, I use long-type ignition plugs which are recommended by Kia My question is: Can I change spark plugs from long to short -type to get rid of the knocking or detonation problem? I've already installed spark plugs (short- type ) and got rid of the problem, but does have a bad effect on the engine later ..?

[@amg3434]

Wow! Best advice ever

[@TheTuningSchool]

We're here to share as much knowledge we gain, as well as our discoveries. Thanks for watching!

[@MrNiceGuyGTL]

I have a 2015 subaru wrx. I use a cobb accessport and put an ETS intake system, an ETS catback exhaust, a mishimoto charge pipe and a turbosmart dual port 50/50 hybrid BOV. I have been using the ETS stage 1 tune on the Cobb website that was removed from their website a while back. Under extreme driving (redlining the car) its stalled on me occasionally on the freeway but starts right back up again. Tonight I started my car and the engine knock on the AP read -5.82. I have to drive this car in a day or 2 because i’m moving. The distance is about 130 miles. What’s wrong with my car?

[@Jandjspeedshop]

Great advice

[@TheTuningSchool]

Thanks! We hope you subscribed for much more. Keep the comments coming!

[@minorpyro69]

GOOD INFORMATIVE VIDEO!

[@TheTuningSchool]

Thank you. We hope you subscribe to our channel for much more. Your suggestions are welcomed!

[@dnawrapsatl]

I think I'm getting false knock on sudden accel. In 1st to 2nd gear. I got negative 8. 48. But during wot pulls I get zero knock. Am I still OK? As long as it doesn't knock at wot?

[@DCFloridasport]

Of all the stuff I clicked off, I left my KS on, and found my solid motor mounts set them off in the first minute of driving lol still aint turning them off tho

[@gman8230]

could this be the reason my head is getting way too hot but my temp gauge never goes past half? i am throwing a code for knock sensor.

[@alitoroganan2442]

can knock happen on a low rpm load and e85? coz i bought an ecu that doesnt support my stock knock sensor,. anyway thanks

[@thisisyourcaptainspeaking2259]

Self-ignited? No. Detonation occurs when the air/fuel charge in the combustion chamber stops burning prematurely. This always occurs following the spark event of the combustion stroke and generally isn't immediately destructive (but should be avoided, especially in high performance applications). Pre-ignition occurs prior to, the spark event and is generally very destructive.

[@ehsanurrahman8812]

Thanks!

[@TheTuningSchool]

You're welcome!

[@mattwalker5251]

very good.

[@TheTuningSchool]

Thank you!

[@sdotcam1]

So my tuner determined that I have false knock in my 5.7 hemi. So now how do I fix the issue now?

[@Fa5_4_lyfe]

Desensitized the knock sensor or sensors

[@vick9333]

What is knock count? What is high and normal (safe) of knock count? Vic3000gt

[@behindthen0thing]

Vic Karpov idk

[@nathannellis6516]

See, I still think it's my sensor in my truck that went bad. Mpg is the same tbh and it's a little guy that, in higher gears and speeds , quiets down , even when I come to a light or stop sign and have stop, it's barely noticeable

[@JanineCeleste]

Is there a probable cause that you can think of as to why a vehicle would start knocking immediately after an oil change when there was no knocking before? We have a 2003 Chevy Trailblazer that rarely gets driven. In fact we only drive it a few times each month just to keep the battery from dying. This vehicle has ran smooth for as long as we've had it, which is about 8 years. I took it in for a an oil change and noticed about 1/2 a block away from the automotive shop that it was knocking, so I took it back. They hooked it up to a little hand held device and told me that it's my timing. They said if I don't change the oil soon enough that in this particular vehicle, it will affect the timing and that it's the belt hitting the side of something. But it just really sounds like a thrown rod. We took it to 2 other shops and just by listening to it, they stated that I needed a new engine. I am having a hard time believing that something about the oil change didn't cause this. There were no engine issues right up until the oil change. Any comments?

[@trevorpatton6377]

The knock you are talking about isn't really the same as in the video but if your engine started knocking immediately after having the oil changed there is a pretty good chance it's related. was the oil pressure light on when you left the shop? if so they probably didn't put any oil in or something happened for the oil pressure to be very low or contaminated.. there are many reasons but the engine is finished for sure.

[@Tsagami]

If the gas is too bad can the the ECU handles the preignition correctly?

[@blow0me]

that depends on the ecu and how it is setup...they are not all equal.

[@rhamliniirhi]

What if you started on racegas, and can't do step 3?

[@backdoormailman]

Add octane boost lol

[@09fatbobmike]

Then its not False knock

[@michaelslack6891]

I'm guessing, to richen afr and then try backing off timing

[@teebksa]

i have tuned my car when i start first tune it count -2.6 next tune -1.3 next tune 0.7 is that mean great and last tune is perfect or i have to make it 0 ?

[@TheTuningSchool]

The only reason to be concerned with such little knock is if you can accurately replicate it. In addition, you should just continue to perform what you are doing in the tune file to bring the knock down consistently every time.

[@mjl6425]

Could running rich from a boost leak cause knock?

[@TheTuningSchool]

A boost leak is an unlikely cause, but there can be a condition called rich knock that occurs where there is so much fuel in the chamber the combustion can’t consume it all. This leaves excess fuel in the Chamber that can then ignite on its own causing knock.

[@piecartbox]

tyvm

[@TheTuningSchool]

yw!

[@paniki_man2512]

with knock retard sensor, is it true that below 1 is still considered normal? i have some people mention about efficient point. and above 2 is considered abnormal?

[@JesusGonzalez-qb4rb]

I have a 2014 Chevy Cruz and it works pretty good but as soon as I turn on the ac the motor starts to make a knocking sound, anyone knows why?

[@TheTuningSchool]

Do you have a scan of it using HP Tuners? thetuningschool.com/product/hp-tuners-gm-vcm-suite-mpvi-pro/

[@RB26PWR2]

😂😂... don’t be a limited octane hero! Knock sensors have a place.. I’m removing my knock sensors on my LS... c16 for the win

[@TheTuningSchool]

Nice!

[@jessetolley3974]

20 people turn their knock sensors off.