Negative STFT numbers, Engine rattle localized to fuel rails?`

My vehicle is a 2003 Ford Explorer 4.0 V6 SOHC engine, 5 speed trans AWD

I've been having issues with a loud rattle lately coming from the engine mostly at idle, depressing the gas pedal at all will make the noise stop.

I used a mechanics stethoscope in the engine bay to try to narrow down where it's coming from. I placed it all over anything I could touch (trying to see if it was timing chain slack), No noise at all close to where the chains are, but as soon as I touched anywhere on either fuel rail it's rattle city, Not so much a consistent tick you'd expect from injectors, more of a faster rattle that gets even faster but more rhythmic as RPMS increase.

My STFT numbers are also more negative now than normal (usually I'd see fluctuations between -6 and 6, but now it's bottoming out around -15%), which means the computer is taking away fuel right, so it's reading a rich condition right? In all of your experiences are these things related or what could be the issue here? I am also getting a rough idle, engine shakes quite a bit when idling, and also a loss of power and hesitation issues.

Thanks for any help!

Any ideas guys? Need to make it through a road trip Saturday and want to make sure all is ok with it,

Thanks

Not sure what the rattle is. But have you checked your fuel pump pressure? Possible your pump is going faulty and not being able to keep up the fuel that is required.

Dave,

I have not done that, how exactly do I go about doing so?

Agree. Check your fuel pressure. The pressure regulators are really the only common failure on the Ford dead head systems.