Death Rattle?

[Sincoln]

This one is strange. Was at a drive-thru, and behind another car. As I inched up to the window, heard what sounded like a hollow tap/knock. Blood ran out of face, and I put it in Neutral and lightly revved it. Hollow tap/knock went up with revs.... Took forever (or seemed like it ) for the girl to hand me the food, and I promptly pulled forward to a park spot. Got out and checked for oil (feared an oil adapter gasket blew too quick to catch) under the car. There was none. Figuring if it was rod or something higher up, the damage was already done, so put it in reverse and pulled out on the street. Engine sounded normal. Felt fine, nothing coming through the firewall or echoing off the pavement. About a mile later, back home. Engine sounds as quiet as normal... no rattle, nothing rpm-based, nothing. I didn't imagine it.

Any ideas? If it was a rod, piston, etc. it wouldn't fix itself. Only things that come to mind is maybe the upper idler pulley, or something with the water pump?

 

[Sincoln]

Looks like it's the idler pulley. It has excess side load play in it. Also, tapping it with a metal chisel gives the same hollow sound. So fingers crossed! And engine oil is still on the mark after almost 500 miles, so hopefully dodged a big ol' bullet there.

 

[FlaOkie]

Good it’s the pulley as opposed to a rod.

I haven’t got around to it yet, but the belt, pulley and tensioner are on my list to be replaced as preventative maintenance.
Months ago I bought jugs of MerconV trans fluid and a new filter. I’ll get around to that soon too.

I will use the excuse that I’m still cutting up trees and cleaning up after hurricane Irma.

 

[Sincoln]

Sorry to hear about Irma. Hope it didn't do too much destruction to you and yours!

Never heard a pulley sound like this. Usually they just grind up. This one created a wobble. Wonder how many have sold their car thinking it had a bad engine.....

 

[Sincoln]

Guess I was wrong. Rattle still there. Either one of the cats has a broken honeycomb i.e. substrate separated from the metal and is loose but can't get past the pipe outlet diameter but occasionally jamming in place, or something metal on the exhaust above the trans is possibly causing it. Rawer gas out the pipe is evident again, like when it had troubled COP.

Anyone know if either cat is solid throughout, or is there a gap between substrates on these? IIRC, some cats have TWO actual substrates like:

Guessing it's the cat higher up as the one that Y's to the single out was solid when I tapped it.