HELP needed to diagnose engine noise
 

Hey guys,

I started getting a strange engine noise the last few days under light acceleration. it sounds like a rattle of some sort but I can't narrow it down. I was hoping to see if anyone could recognize it and point me in the right direction to solving. I'll post it in a video, the sound is very obvious. I'm hoping I haven't done anything too serious.
Thanks in advance.


https://youtu.be/dzEpbNnnfVk

hmmm......are you referring to the "ticking" or "light knocking" sound the engine is making .. ??

What, if anything, have you done to the engine within the last few days..??

Can you isolate the sound with a scope/rod/tube ..??


humfrz

Thanks for your response. The metallic banging sound was what I was referring to. This is a new sound.

How would I isolate the sound? Would I hold a tube near certain parts of the engine and see if the sound is amplified?

I changed my oil two weeks ago. That was the last thing I did to the engine. I noticed this sound when I returned from leaving my car at the airport for a day. It's middle of summer here if that helps.

bump :)

Are you sure it is not the wonderful sound of direct fuel injection? A few days after I got my car I had it towed with the 6 free months of subaru protection or whatever because I thought the engine was knocking. It makes a rattling noise when I lug the engine on a gentle take off. This is normal but was alarming for me

Crickets...

Yeah pretty sure. It got a lot worse today. Got a mechanic out who thinks I've spun a baring....i'll try get a second opinion.

Kinda sounds similar to what I had and went through Jan 1st.

https://youtu.be/6zrsWeDxsIE

Dealer said rod knock. Didn't want to pay the $1875 for a tear down and another $3000+ for a new short block and install.
I just ended up trading it in for a 2017 BRZ.

I assume you rechecked oil levels today just to be sure?

@humfrz is referring to a mechanics stethoscope. Touch the stick to different parts in the engine bay to see where it's the loudest. You might be able to identify which bank is the problem or maybe some other part like transmission, but since it's so loud it might not help. Or might deafen you... :iono:

To attempt to isolate the sound, back-in-the-day, we used to use a long screwdriver or metal rod with a knob stick on the end of it and place the rod different suspected places, with an ear to the other end, in an attempt to help isolate the source of the sound.

They actually make store bought mechanics stethoscopes that can be used.

Some just use a tube ...... making like its a sound tube.

However, the FA20 engine is soo noisy, it would be difficult to isolate any one sound.

Back-in-the day, I would have suspected something in the valve train is lose or out of spec. But here lately, the sound of a rod knocking (because of a spun bearing) seems to be the popular sound.

If it's a rod knocking, the sound would be heard throughout the block, when scoped. A valve messing up could be isolated from one bank to another.

Is there any way to disconnect the SC, and still get the engine to run, to see if the SC is making the noise ....??

Yep, a second hands on opinion would be in order.

I hope it turns out to be minor.

Please keep us posted.


humfrz

Is it an automatic?

Good question!


humfrz

knock knock.
Who's there?

My only question is whether it is upper engine or lower engine. I'm not going to diagnose for sure from a YT video, but someone already diagnosed it in person.

How is your AFR? Look at fuel trims too and do you have any CEL, what tune are you using? If the engine is running very lean it could be pinging, but most likely it is like that mecahnic said and a rod knock

It's a manual guys. It was diagnosed in about 3 seconds. It got significantly worse since I first posted. Its Lower engine. Rattling BAD. I youtube 86 spun bearing noise after they diagnosed and it sounded the same. IL need to get it towed anywhere at this point forward so it will be hard to get second opinion. The mechanic came to me today which was way above and beyond.