Odd rattle

[GEE-OTTO]

Just recently my 08LGT developed a rattle at part throttle out of boost but but before getting into boost, similar to valve train chatter when you are lugging the engine.  
 

Checked for low oil it’s fine near the top of the operating range per the stick(cold and hot). So I go out driving and it seems to only occur around 2300-2800 RPM part throttle, when I increase throttle it goes away doesn’t happen at lower or higher than that RPM range. 
 

I once read that timing tensioners/idlers can cause this as they fail. Have any of you had a similar issue? Could it be a jumped tooth? 

[xt2005bonbon]

I had a timing belt tensioner fail on me while driving . Somehow, I did not bend any valve. It was making an awful knocking sound (on the timing belt cover) until its bolt sheared off the tensioner bracket. So, if you suspect that is it, better check it quick!

A video would also help.

[silverton]

58 minutes ago, xt2005bonbon said:

I had a timing belt tensioner fail on me while driving . Somehow, I did not bend any valve. It was making an awful knocking sound (on the timing belt cover) until its bolt sheared off the tensioner bracket. So, if you suspect that is it, better check it quick!

A video would also help.

You got lucky! Same thing happened to me on a 251 and bent all 16

[m sprank]

Does it happen as load increases?  Like you are cruising and a hill comes up and you add throttle (lightly) to maintain speed going up the hill?  As you do so you hear the "rattle" and it goes away after you let off throttle back to cruise?

[silverton]

Edit: LMAO. m sprank was replying to OP, not me. LOL

 

I wasn't driving when mine went, but I do have dashcam footage of it with audio. My buddy who was driving, just cruising with traffic on 405, is very inclined to automotive things and he didn't notice anything weird until it just starts cutting out.  it's a long'ish video I never bothered cropping, if you're interested in watching I'll work on that.

Edited July 13, 2023 by silverton

[m sprank]

Dont want to ginx the op, but sounds like rod knock.  When turbo  Subies dont go boom, many times they exhibit the 1st signs of knock under these circumstances. 

[rhino6303]

It could be detonation. Any tuning or physical changes you've done recently? General modifications?

[GEE-OTTO]

13 hours ago, m sprank said:

Does it happen as load increases?  Like you are cruising and a hill comes up and you add throttle (lightly) to maintain speed going up the hill?  As you do so you hear the "rattle" and it goes away after you let off throttle back to cruise?

I think yes! It would go away above or beyond that load range. And that makes sense as my first thought was “why are my valves rattling” 

Ill get a video to show the sound. 

2 hours ago, rhino6303 said:

It could be detonation. Any tuning or physical changes you've done recently? General modifications?

No mods and no tuning changes. Timing has 62k mikes on the parts but everything else is original. No changes in oil or fuel consumption and AP monitors are normal. 

Appreciate the comments!! 

 

[m sprank]

Watch your knock sum during the event.  Unfortunately, sounds like the beginning of rod knock.  Similar to a ball peen hammer tapping a metal block. 

[GEE-OTTO]

So update had a 600 mile stint of driving for various summer adventures between VA and WV. I added the Knock sum to the AP to monitor it and at various times it would be at 7, 23, 34 then reset. One thing I recalled after reading the comments I filled up at a no-name gas stating when this started, I typically run 93 V-Power. I ran that tank out after this post and filled up with V-Power at my normal Shell, no pronounced rattle like before. 

If it is the start of the end, I can't complain, 227K miles and counting of majority smiles and worry free operation. Also shopping a VB WRX in Ice Silver Metallic to replace this 08 LGT. Ill keep yall posted! 

[m sprank]

Could be BAD knock from VERY BAD gas.  Should know in a few tanks.  At 227k, you got your monies worth out of that EJ255.