I have a 2006 F-250 V10 and noticed today a rattle sound coming from my engine, when under load around 2500 rpm. This rattle sounded like marbles in a tin can... I don't know if this is detonation or not because the check engine light never came on. My question is: is this engine knock, and how do I fix this?

I've heard of water/methanol injection and was wondering if this would work?

 

You sure it's coming from the engine, and not something else? Perhaps exhaust heat shield, or maybe the infamous torque converter inspection plate?

 

I'm pretty sure its coming from the engine... I checked all of the exhaust and heat sheilds for leaks, cracks, loose sections, etc.. Everything was fine! I also tried watching videos that had the sound of engine knock and it sounded almost exactly the same. Could bad fuel cause this?