Been having a knocking sound/ rattle which I believe is coming from somewhere within the engine bay (although I'm not 100% sure). The sound comes on between 3000rpm to 4500rpm, and is only present under load (no sound revving in neutral). I had initially thought it was engine knock or misfire of some sort and have changed all the fluids on car, spark plugs, air filter, and even decarboned the intake valves (walnut blasting). The sound is still present at the said rpm, strangely, there are no codes and CEL, car feels fine apart from the knocking sound. The car doesn't hesitate or judder even between 3000rpm to 4000rpm. The knocking however, goes away on longer drives for some reason. I'm starting to suspect it isn't a misfire or engine knock but rather something else rattling. This has been puzzling me for quite some time now and any help would be much appreciated.

 

Could be your serpentine accessory belt and tensioners.

 

Apologies, forgot to add that serpentine belt and fuel filter are new too. Checked the tensioners while changing the belt and they seemed fine.

 

Does this knocking sound make any sort of feelings in the steering wheel or floorboard or in your drivers seat?

 

Not really. It kinda sounds like timing chain rattle although I can't be 100% sure.

 

Rattling sound could very much be your rusted out exhaust shields. These things tend to make buzzing noise at certain RPMs when they go bad.

 

Wouldn't those rattle even when in neutral and not just when there is load?

 

Take a look at the carrier bearing/mount for the driveshaft.