Rocks in the engine

Alright well heres my troubles, when I start it up, it sounds like their are rocks in the engine/water pump (general are) Im not sure what it is cause i havent had any serious problems. Their was a heart stopper when I changed the spark plugs out and found a hole in one and an actual pebble in a chamber(had just got done mudding and was cleaning the engine, found out later that I got alot of water in the chamber so I was running on 7, went to the shop and had them change the plugs) found no damage done but definitly a bad one. So I dont know it only seems to happen when its cold and only when I first start it. Its kinda a high pitched scream with some rumbling like their are broken parts rolling around (like the sound when you vacum up lose rocks into a shop vac) Also their is nothing wrong with the truck, accelerates superbly, stops great, belts are good, shes pretty clean. Also she kinda idles weird, like she might be starved for air but not, I had a problem like this before but really bad where my truck would lug alot just ideling and it would actually make the truck rock when ideling, so I took it to the shop cause it bugged the crap outta me, it was the EGR valve and replaced that and it was all good. No error codes, no check lights, just the weird noise and a lil bit of rough idel. Any help would be appreciated.

Specs:
1997 F150 Single cab
5.4L Triton
121,000+ miles

Take the belt/belts off and start it. If the noise goes away, check the idlers/tensioner, alt, water pump.....ect. You may have a bearing going out in one of them. If the noise is still there with the belts off, use a long screwdriver, piece of pipe , or something similar, and hold it to your ear, and different parts of the engine to isolate the noise.

Yeah definitly, I remember replacing one of the Idler pulleys about a year ago might be time to replace the other one, thanks for the response

Yeah definitly, I remember replacing one of the Idler pulleys about a year ago might be time to replace the other one, thanks for the response

Since it occurs at start up I am led to believe that you have an exhaust manifold leak. The 5.4 is notorious for this, as a matter of fact mine has the same problem now.

The erratic idle is probably the tab valve.

My F-150 had a lot of valve noise until I switched to a thicker oil. I changed at 1000 miles and at 4000 miles I went to a thicker oil. If using 5W30 go to 10W30 or 15W40. It rattled heavily until full oil pressure was obtained.