Lately I've been hearing a very low knock coming from the engine at idle. It's very noticeable if you have the car in neutral and rev it slightly to 1500 and let off the gas. It's a completely different noise than what the fuel injectors are making.
I'm not sure if I'm mistaking it for something normal on the MS6 or not so I wanted to get some opinions. Can anyone else duplicate this? It's not noticeable while driving, and you can really only hear it if the radio is off and everything is very quiet.
Full Version: Engine knock at idle
Mazda6 / Atenza > Technical / Performance / Model > Mazda6 1st Generation (2002-2007) > Mazdaspeed6 > Speed6 Engine/Drivetrain
Is it a knock or a clicking? Like tap-tap-tap-tap? Or even a tick-tick-tick?
Also, what grade gas do you use?
Also, what grade gas do you use?
Even engines that knock dont do it if you rev them and then let off the throttle. It has to be something else.
The only thing that I can think of off the top of my head is valve lash. A frayed timing or serpentine belt *might* cause something that sounds similar if it is hitting something, but that is unbelieveably remote because it probably would have broken already.
If you put a marble in a mason jar and shake it as fast as you can, that is what engine knock, or preignition, sounds like. Engine knock is also not consistant, it skips a beat when it should be knocking. Valve clatter, caused by incorrect valve lash can sometimes be very quiet, but is never goes away and you can set a watch to it because each one of the ticks is that predictable.
On a mechanical valvetrain engine like ours, some noise is acceptable. If it gets as loud as the injectors, I would take it in.
I guess I should ask, does it happen in neutral + driving or just while driving?
The only thing that I can think of off the top of my head is valve lash. A frayed timing or serpentine belt *might* cause something that sounds similar if it is hitting something, but that is unbelieveably remote because it probably would have broken already.
If you put a marble in a mason jar and shake it as fast as you can, that is what engine knock, or preignition, sounds like. Engine knock is also not consistant, it skips a beat when it should be knocking. Valve clatter, caused by incorrect valve lash can sometimes be very quiet, but is never goes away and you can set a watch to it because each one of the ticks is that predictable.
On a mechanical valvetrain engine like ours, some noise is acceptable. If it gets as loud as the injectors, I would take it in.
I guess I should ask, does it happen in neutral + driving or just while driving?
QUOTE (Corpus_Speed6 @ Sep 28 2008, 03:15 AM) 
Even engines that knock dont do it if you rev them and then let off the throttle. It has to be something else.
The only thing that I can think of off the top of my head is valve lash. A frayed timing or serpentine belt *might* cause something that sounds similar if it is hitting something, but that is unbelieveably remote because it probably would have broken already.
The only thing that I can think of off the top of my head is valve lash. A frayed timing or serpentine belt *might* cause something that sounds similar if it is hitting something, but that is unbelieveably remote because it probably would have broken already.
corpus speed6
valve lash is not adjustable, we have a timeing chain not a belt......
just to let you know
Valve lash is the distance between the lifter bucket and the cam, it is adjustable.
Valve timing is set with the chain and sprocket, on our car the intake sprocket appears to be infinately adjustable because it has no key. The exhaust one does not appear to be adjustable.
Valve timing is set with the chain and sprocket, on our car the intake sprocket appears to be infinately adjustable because it has no key. The exhaust one does not appear to be adjustable.
QUOTE (Turbo6Girl @ Sep 27 2008, 08:23 PM)
Is it a knock or a clicking? Like tap-tap-tap-tap? Or even a tick-tick-tick?
Also, what grade gas do you use?
Also, what grade gas do you use?
It's a tap-tap-tap. I use 93.
QUOTE (Corpus_Speed6)
Even engines that knock dont do it if you rev them and then let off the throttle. It has to be something else.
The only thing that I can think of off the top of my head is valve lash. A frayed timing or serpentine belt *might* cause something that sounds similar if it is hitting something, but that is unbelieveably remote because it probably would have broken already.
If you put a marble in a mason jar and shake it as fast as you can, that is what engine knock, or preignition, sounds like. Engine knock is also not consistant, it skips a beat when it should be knocking. Valve clatter, caused by incorrect valve lash can sometimes be very quiet, but is never goes away and you can set a watch to it because each one of the ticks is that predictable.
On a mechanical valvetrain engine like ours, some noise is acceptable. If it gets as loud as the injectors, I would take it in.
I guess I should ask, does it happen in neutral + driving or just while driving?
The only thing that I can think of off the top of my head is valve lash. A frayed timing or serpentine belt *might* cause something that sounds similar if it is hitting something, but that is unbelieveably remote because it probably would have broken already.
If you put a marble in a mason jar and shake it as fast as you can, that is what engine knock, or preignition, sounds like. Engine knock is also not consistant, it skips a beat when it should be knocking. Valve clatter, caused by incorrect valve lash can sometimes be very quiet, but is never goes away and you can set a watch to it because each one of the ticks is that predictable.
On a mechanical valvetrain engine like ours, some noise is acceptable. If it gets as loud as the injectors, I would take it in.
I guess I should ask, does it happen in neutral + driving or just while driving?
I can't hear it over road noise or even above the engine if it's above 2000 RPM. The only time it's noticeable is while parked. I found a thread on another forum about a TSB on these cars because of a sound at idle. I'm not sure if it's related, but I'm going to look into it more.
QUOTE (MicaBlackMS6 @ Sep 28 2008, 12:50 PM)
No, you can hear this over the ticking of the injectors. Thanks for that link, I'll look into that!
Definitely sounds like cam shaft tick, mine does the same thing and is only noticeable at idle. If you have warranty get the TSB done and see if that fixes it.
It doesn't fix it, I have had it done.
I wouldn't worry to much about it.
I wouldn't worry to much about it.
QUOTE (Corpus_Speed6 @ Sep 29 2008, 03:03 AM)
It doesn't fix it, I have had it done.
I wouldn't worry to much about it.
I wouldn't worry to much about it.
That's good to know, my warranty was voided before I could get it so atleast I know I'm not missing out.
Got my car back from the dealer and they're saying it's a normal noise that is coming from my high pressure fuel pump. Still waiting for my buddy to stop by with his MS6 so I can listen for it on his car.
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