Couldn’t find anything related to this unless I just didn’t look hard enough (although I’ve checked almost every forum there is known to man...)

I’ve got a knock in my engine, and I’m hoping it’s an way fix and nothing super expensive. Every once in a while I have to drive about an hour to the in-laws house and long story short after driving through the back roads with red lights and stop signs everywhere, I’ll hear this knock when I idle at a light or stop sign. The truck doesn’t run hard when it knocks, doesn’t shake, my oil pressure is fine, and only does it for about 10 minutes. Then by the time I get to my destination, it’s stopped and I can’t seem to figure out where it’s coming from other than under the hood (obviously...) It's not a rhythmic knock either, which is weird.

<--- Here's the video of it knocking. Doesn't sound like a knock on other videos I've watched. I'm completely stumped.

 

That to me sounds like a frequency thats not equal to RPMS or even 1/2 rpms.(bottom end or valvetrain)

Is it possibly something in the "FEAD" (front end accessory drive)? I'd pull the belt and turn everything by hand and feel for looseness or something that has to much friction to turn. Also check the belt.

If you think its inside the engine.. take a hose or buy a cheap stethoscope from HF and find out where in the engine the noise is loudest.

 

I finally caught it today at the gas station as I was pulling in. I did a radiator flush and changed the oil and I think the constant idling and revving throughout the day warmed it up enough as if I was driving a long period of time. Sounds like it's coming from underneath the headers.
So, now, my guess is a misfire somewhere and I need to replace the spark plugs...maybe? I'm also guessing the guy I bought it from didn't keep too good of maintenance because the radiator fluid was BURNT ORANGE. The oil was black as night too. So if all of that was nasty, I think it's safe for me to assume that about the spark plugs, just haven't had the chance to go under the hood again and pull em out and check em.

 

That sound to me is NOT pre-ignition. It's a solid metal on metal sound IMO.

Under the headers... ok maybe a lifter is sticking when oil is hot enough? Maybe its sticking intermittently and so there is no repetitive knock, knock, knock?

In my experiences that type of sound is either... a rod bearing, timing chain, or a lifter.

 

Not an engine knock in my opinion, too intermitant

Almost sounds like a broken fan belt slapping metal

 

My first impulse was FEAD too. But he says noise is under the exhaust manifold. (I assume a hose was used to pinpoint the source)

 

Well, engine pulled a code the other day. Plugged into the truck and it pulled a "Cylinder 1 misfire."

Replacing spark plugs this weekend....