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Acura EL
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Discussion Starter #1 (Edited)
So recently I’ve started to notice this knock/ tapping sound coming from my engine not long after I got it tuned. it sounds A bit deaper of a Tap from valve tap and it doesn’t quite sound like It’s coming from the bottom of the block or the top but somewhere in the middle near the intake manifold.. anyways the sound goes away if you rev up the car and just after you drive it and my oil pressure still remains to be the same (20psi on idle). It also only comes when the car is at operating temp.

It’s a D16Z6

Videos of the sound:
https://youtu.be/FJD3JeFkN9E

https://youtu.be/XWMAumj0pZU
 

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93 Civic HB SI
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When you went low with the camera into the wheel well, it almost sounds like rod knock. Did you build the engine internals for more power or is it a stock bottom end?

Your location says your in Montreal, not sure how far one is but go to Princess Auto or equivalent and buy a $3.99 mechanics stethoscope and use it to narrow down the location of the knock. It doesn't sound like crankshaft, but it is also deeper in tone than valvetrain noises. You also mentioned you don't feel it is valvetrain because it sounds deeper. A stethoscope will get you much closer to the culprit without teardown and inspection.
 

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Acura EL
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Discussion Starter #5 (Edited)
When you went low with the camera into the wheel well, it almost sounds like rod knock. Did you build the engine internals for more power or is it a stock bottom end?

Your location says your in Montreal, not sure how far one is but go to Princess Auto or equivalent and buy a $3.99 mechanics stethoscope and use it to narrow down the location of the knock. It doesn't sound like crankshaft, but it is also deeper in tone than valvetrain noises. You also mentioned you don't feel it is valvetrain because it sounds deeper. A stethoscope will get you much closer to the culprit without teardown and inspection.
Engine has a built bottom end. I’ll see if I can find one, I thought it would be more than just 4 bucks but anyways... if it was rod knock wouldn’t I see other signs such as oil pressure or metal shavings in the oil? I’ve done a couple pulls with the engine making this noise and it hasn’t gone louder. It’s also most noticeable after the car has been idling for 1-2 minutes

Edit: so I did the old trick with a wooden stick and it seems to be maybe a little bit more pronounced when I put it against the valve cover and listen than the oil pan
 

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93 Civic HB SI
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You are right, you should see some signs of metal contamination in oil if it truly was some sort of rotating assembly clearance issue. Run the engine till the oil is warm-ish and drain it into a catch can with a coffee filter on it and check for anything suspect. Also remove the oil filter and dump out the contents into the coffee filter as well, to see if any metal particulate is being caught by the oil filter.

Oil change is a cheap diagnostic tool, and will make you feel much more confident about saying there is nothing wrong in the bottom end.

Yes, those stethoscopes are stupid cheap from Princess Auto/Harbor Freight, whatever your favorite chinese tool warehouse might be called lol.

If you say you hear top end noise with the wooden dowel, I would pull the valve cover and check valve adjustment, again as a diagnostic tool to aid in narrowing down the source of the noise. Valve cover gasket and some oil-resistant RTV for the cam cap corners is cheap to replace.

It's all cheaper than 1 hour labor at a shop and you'll get more work done than a shop would for the same price lol.
 

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Discussion Starter #9 (Edited)
You are right, you should see some signs of metal contamination in oil if it truly was some sort of rotating assembly clearance issue. Run the engine till the oil is warm-ish and drain it into a catch can with a coffee filter on it and check for anything suspect. Also remove the oil filter and dump out the contents into the coffee filter as well, to see if any metal particulate is being caught by the oil filter.

Oil change is a cheap diagnostic tool, and will make you feel much more confident about saying there is nothing wrong in the bottom end.

Yes, those stethoscopes are stupid cheap from Princess Auto/Harbor Freight, whatever your favorite chinese tool warehouse might be called lol.

If you say you hear top end noise with the wooden dowel, I would pull the valve cover and check valve adjustment, again as a diagnostic tool to aid in narrowing down the source of the noise. Valve cover gasket and some oil-resistant RTV for the cam cap corners is cheap to replace.

It's all cheaper than 1 hour labor at a shop and you'll get more work done than a shop would for the same price lol.

I’ll give it a shot! I was thinking of doing the oil pan gasket anyways so I’ll check for containment in the actual pan when I do it. Is it possible it’s piston slap? Like it’s hitting the cylinder walls?

A friend of mine told me that it could be an injector, apparently they have a knock sensor for when they fail, but what’s only what I’ve been told.
 

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Good, I'm glad you are willing to put some time in to investigate! It is better peace of mind. If it is internal damage, it's good to catch it now and attempt to prevent it further. Better to tear down and investigate sooner rather than later and see if things can be salvaged.

About what you said about the knock sensor. If your engine is equipped with a knock sensor, the knock sensor is only used for detecting damaging in cylinder detonation/pre-ignition events. It will be in no way related to malfunctioning/noisy injectors, although a dirty injector restricting fuel will cause lean conditions and make pre-ignition more likely. The knock sensor is used for preventing engine damage caused by pre-ignition, not much else.

Mind you, if any internal mechanical metallic knock is loud enough and specific enough of a frequency it can false-set off the knock sensor and the ECU will pull timing because of it, thinking it is detonation/pre-ignition.

Knock sensors actually detect sound waves produced from a pre-ignition event that propagate through the metal, originating from the rotating assembly. The knock sensor is usually placed high up on the outside of the block, close to where the combustion chamber would be with a piston at TDC so it can sense any pre-ignition event sounds as quickly as possible and report to the ECU.

The knock sensor is built to detect only a certain resonant frequency. This frequency is found by the OEM engineers inducing detonation/pre-ignition and then measuring the sound of the knock that the engine makes. Different engines will produce similar but harmonically different pre-ignition frequencies simply due to the different design characteristics of each engine, so the sensors are tailored to the ENGINE based on this R&D from the manufacturer.

I've worked on a few vehicles that came in for low power complaints, none of the owners mentioned anything about a funny engine sound when any of them first came in. I test drove them and the damn engines had this mid range metallic knocking sound, not too deep but not too high pitch, but apparently around or about the perfect resonant frequency to drive the knock sensor(s) crazy. The ECU would pull timing and engine power would fall completely flat. Serious internal mechanical damage was present.

Installed reman engines, and sure enough no more mechanical engine knock, no more unhappy knock sensors and full power.
 

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Acura EL
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Discussion Starter #12
Good, I'm glad you are willing to put some time in to investigate! It is better peace of mind. If it is internal damage, it's good to catch it now and attempt to prevent it further. Better to tear down and investigate sooner rather than later and see if things can be salvaged.

About what you said about the knock sensor. If your engine is equipped with a knock sensor, the knock sensor is only used for detecting damaging in cylinder detonation/pre-ignition events. It will be in no way related to malfunctioning/noisy injectors, although a dirty injector restricting fuel will cause lean conditions and make pre-ignition more likely. The knock sensor is used for preventing engine damage caused by pre-ignition, not much else.

Mind you, if any internal mechanical metallic knock is loud enough and specific enough of a frequency it can false-set off the knock sensor and the ECU will pull timing because of it, thinking it is detonation/pre-ignition.

Knock sensors actually detect sound waves produced from a pre-ignition event that propagate through the metal, originating from the rotating assembly. The knock sensor is usually placed high up on the outside of the block, close to where the combustion chamber would be with a piston at TDC so it can sense any pre-ignition event sounds as quickly as possible and report to the ECU.

The knock sensor is built to detect only a certain resonant frequency. This frequency is found by the OEM engineers inducing detonation/pre-ignition and then measuring the sound of the knock that the engine makes. Different engines will produce similar but harmonically different pre-ignition frequencies simply due to the different design characteristics of each engine, so the sensors are tailored to the ENGINE based on this R&D from the manufacturer.

I've worked on a few vehicles that came in for low power complaints, none of the owners mentioned anything about a funny engine sound when any of them first came in. I test drove them and the damn engines had this mid range metallic knocking sound, not too deep but not too high pitch, but apparently around or about the perfect resonant frequency to drive the knock sensor(s) crazy. The ECU would pull timing and engine power would fall completely flat. Serious internal mechanical damage was present.

Installed reman engines, and sure enough no more mechanical engine knock, no more unhappy knock sensors and full power.

Hmm, so I guess it ain’t that then.. the engine still has full power and I’m still able to do those nasty pulls.. anyways I’ll send an update with what I find from the oil!
 

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well the z6 doenst have a knock sensor. so its not going to pull timing if knock sensor is tripped.

it does sound like rod knock from the 2nd video. for sure check the oil. if you do decide to pull the pan and change your gasket go ahead an try to shake the big end of the rods.

if you can move the rod then its spun if its snug then your good.

first video just sounds like loud injectors. ddont think its piston slap as that usually gets quieter as the engine gets warmer.
 

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Discussion Starter #14
UPFATE:
Ok so I pulled the pan today as well as inspecting the oil.. nothing in the oil except for a few small bubbles that I at first mistook to be metal shavings. As for the rods itself, I tried pulling on all of them to see if there was any play, no up and down play whatsoever. There is some side to side play on them however. Is that normal?

Video:
https://youtu.be/YvmESjxBcgM
 

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Side to side is totally normal.

Did you pull the oil filter and dump out the contents? Sometimes it's worth it to cut the filter open and check out the element, as the element can be really efficient at catching larger particles. You can use a large screw-type tubing cutter and literally slice open the filter can and pull out the element for inspection. But, if you didn't see any oil glitter you're probably OK.

If you don't see anything, then looks like you're in the clear! One other thing I can think of is looking up at the piston/cylinder wall from underneath.

A friend of mine had someone else assemble his high compression D16Z6 setup, and the dude assembling it must have been high as hell or something (these other guys were usually baked all the time lol). The C-Clip holding in the floating wrist pin fell out (or not installed couldn't really tell, it was not in the pan nor were pieces of it) and the wrist pin moved out and started making contact with the cylinder. It started out as a light tapping, then it started smoking blue after a while, then got to a point where it would cloud up an entire neighborhood before the cylinder lost a ton of compression and started misfiring.

I guess just be on the lookout for blue smoke, if OK then just make sure your engine is warm before you go to hammering on the throttle. I would perform valve adjustment just for the hell of it! I can't really think of anything else causing that type of sound other than what has already been mentioned! Good luck going forward!
 

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Discussion Starter #16
Side to side is totally normal.

Did you pull the oil filter and dump out the contents? Sometimes it's worth it to cut the filter open and check out the element, as the element can be really efficient at catching larger particles. You can use a large screw-type tubing cutter and literally slice open the filter can and pull out the element for inspection. But, if you didn't see any oil glitter you're probably OK.

If you don't see anything, then looks like you're in the clear! One other thing I can think of is looking up at the piston/cylinder wall from underneath.

A friend of mine had someone else assemble his high compression D16Z6 setup, and the dude assembling it must have been high as hell or something (these other guys were usually baked all the time lol). The C-Clip holding in the floating wrist pin fell out (or not installed couldn't really tell, it was not in the pan nor were pieces of it) and the wrist pin moved out and started making contact with the cylinder. It started out as a light tapping, then it started smoking blue after a while, then got to a point where it would cloud up an entire neighborhood before the cylinder lost a ton of compression and started misfiring.

I guess just be on the lookout for blue smoke, if OK then just make sure your engine is warm before you go to hammering on the throttle. I would perform valve adjustment just for the hell of it! I can't really think of anything else causing that type of sound other than what has already been mentioned! Good luck going forward!
Well I did a compression test not long ago, maybe like a week or two ago, and the average compression was around 160 but I’ll check again! And yeah my car does puff blue smoke but only on cold starts (probably valve seals). Hopefully it isn’t an issue like your friend’s 😅
 

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Discussion Starter #17
OK so a little update everybody,

Two days ago I did an oil change on the car and decided to put some thicker oil right after I pulled the pan (might as well right?). I ended up putting 15w-50. Car still running great however the sound is still there.. it definitely sounds like it’s coming from the head now. One weird thing about the sound is that when I decide to do pulls in the car the sound goes away for a short bit after I pull over to let everything cool down.
 
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