Possible engine knock

[PeraFrqct]

hi! I’m new to the Subaru forums and also working on Subarus. There is this sound that my engine makes when warmed up (still prevalent when cold but not to the same degree). I’d describe it as a warble or a shaky sound. If anyone knows what it could be please let me know. I have a video of the sound attached.

 

[PeraFrqct]

Ok so I was told by someone I know it could be something to do with the valve train. I listened beneath the oil pan I don’t hear it coming from there, so it makes me think it’s not rod knock.

 

[Ecmbuster]

No year, make, model, engine size, transmission type?
Compression test?
Engine coolant leak?
Miss-fire monitoring?
Recorded fault codes?
Valve lash check?
"and also working on Subarus"

 

[PeraFrqct]

My car is a 2013 Impreza with a 2 liter fb20 and 5MT. I have not done any tests but there are not coolant leaks or misfires as far as I know. The only fault code that could be relevant is C1422, VDC interruption for engine convenience, but I doubt it.

 

[Ecmbuster]

"C1422, VDC interruption for engine convenience" is because the engine management system recognized a fault code.
Inspect the "Freeze Frame Data" for the criteria that created the fault code.
Did anyone perform the tests that were mentioned?
Was the timing belt inspected?

 

[PeraFrqct]

Freeze frame doesn’t indicate any fault, and vdc lights are not on. No one has done any of the tests you mentioned. This engine has a timing chain.

 

[Ecmbuster]

Subaru Legacy BN/BS (2015-2019) Service Manual - Dtc c1422 vdc interruption for engine convenience - Diagnostic procedure with diagnostic trouble code (dtc)

www.sulegacy.com

That fault can also be recorded if the ECM is not communicating correctly.
The fault will usually make the ABS and VDC not to operate or function.
OBD II scan tools will not properly scan all network controllers.
Subaru uses the SSM protocol (Subaru Select Monitor)

You're welcome

 

[PeraFrqct]

Thank you, but that still doesn’t answer my original question about the engine noise. I’m pretty sure that a vdc fault would not lead to that kind of engine sound.

 

[Ecmbuster]

Obviously the noise is evident if the engine / transmission is rotating.
You can also have an issue with the transmission or connection to the VDC control.
I'm pretty sure I have a very deep understanding of how a Subaru works, behaves and have tested / repaired plenty with 100 % success.
Valve train noises have difficulty travelling to an oil pan filled with oil.
Valve train noises are heard and felt at the engine valve covers.
That's why I developed a PIEZO sensor to measure the frequency / noise down to the individual cylinder or offending item with an oscilloscope many years ago.
IE: http://www.vems.hu/manual/vemstune/help2/htmls/v3/v3_knock_control.html
Once again:
Compression test?
Engine coolant leak?
Miss-fire monitoring?
Recorded fault codes?
Valve lash check?
Added:
Clutch?
Rotating gears?
Out of balance components?
Engine:
MAF values compared to Volumetric Efficiency
Variable Valve Timing following each other in any RPM
PCV valve
EGR valve sticking
Throttle body cleaning and reset
Intake and or vacuum leaks

A VDC fault is an indicator that records and disables part of the engine management system / features.

 

[Niko]

Did you ever get this sorted? Having the same sound on my Subie

 

[PeraFrqct]

Did you ever get this sorted? Having the same sound on my Subie

I took it to several shops and they all said it could just be a regular Subaru sound. How many miles is on yours? I have a feeling with age these motors tend to just wear down faster.