my 1999 3100 53K Miles has a knock that is not in sync with the engine rotation, and speeds up from idle to about 2000 rpm, then it dissapears when accelerated further. At all speeds it is not in sync with engine rotation. It also is not always there. Iw will be there for 30 minutes then gone for days. I cant find answers. Is there any websites that would have soundclips that I could listen to, to help me identify it? I am lost. I posted here before and really didn't get many answers so I am trying again. Thanks
Help with engine knock
- Thread starter HACCOFFICER
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You say it's not in sync with engine location, but is it in sync with something else, the tranny maybe? Wheels? Does it change depending on gear, or whether the clutch is depressed? Does it happen only when moving? Can you tell where it is coming from? How loud is it? Deep metallic knock, light tinny knock, what kind of knock?
- Glenn
- Glenn
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You've got to have some co-action going on. There can't be an asynchronous knock. Even if it's not related to the cause ..it has to be caused by a harmonic or something. This goes for buzzing exhausts ..to whatever (I really have a very hard time thinking of an exception beyond something that would rattle in the wind
).
As glennc suggests ...alter the driving mode when the noise is present. Sway the car ..put it in neutral ..lightly depress the brake pedal...etc. This will, at least, eliminate certain things from the mix. Observe temperature (ambient) and other environmental conditions (did it rain the night before ..very cold). Is the car always in motion when this occurs. When it's occuring ..have you stopped? Did the noise stop as well?
As glennc suggests ...alter the driving mode when the noise is present. Sway the car ..put it in neutral ..lightly depress the brake pedal...etc. This will, at least, eliminate certain things from the mix. Observe temperature (ambient) and other environmental conditions (did it rain the night before ..very cold). Is the car always in motion when this occurs. When it's occuring ..have you stopped? Did the noise stop as well?
It does it when I am parked (haven't been able to hear it yet moving. Its sounds like a deep knock, as if a hammer was ramdomly hitting the engine. Sound like its coming from the top end however I can't be certain being how sound travels in that cars engine compartment.
Would Spark knock or re ingnition sound like this, and out of synce knocking?
Sounds like bad spark knock/detonation to me.
It won't be in sync with anything, becuae it's uncontrolled combustion.
It won't be in sync with anything, becuae it's uncontrolled combustion.
But even pre-detonation happens at a specific point during compression. I agree with GA: Likely the sound is in sync with something, but doesn't occur every revolution. Then multiply this effect by several cylinders and it could appear to sound totally random. Is this engine prone to piston slap?
Engine does have piston slap, however that goes away at 150 degrees or sometimes 160 depending on outside temps. The knock is gone again. Has not returned in a day or so. Thats what it does though, goes away for awhile then returns and knocks for a trip or two then goes away.
My timing belt tensioner on my VW would make similar noises when the bearing was going bad. The knocks would appear at random and would not seem related to engine speed. Try checking bearing play for any accessories that are engine driven.
I was in that area listening and the thing about my engine is you hear the knock in one area, you move position then it sounds like its coming from somewhere else. The sounds travel like crazy. I was thinking spark knock, or something.
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My timing belt tensioner on my VW
This did give a (apparently) random "whack" when it hit the cover on my 79 diesel ..but I knew where it was coming from.
This did give a (apparently) random "whack" when it hit the cover on my 79 diesel ..but I knew where it was coming from.
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