intermitten knocking

so i replaced the idler pulley this morning and then i started it back up and there was a loud knocking like valve knock but then it went away after a few minutes and then it did it again and went away? what is it? any ideas?

A bit more detail, please. Did you look under the hood to try to find it?

well most of the time it does it when its cold. but its goes up and down with the RPM's. its a loud clicking. and i did look under the hood and there is nothing obviously wrong.

So this knocking, did it appear after you changed the idler pulley? If it wasn't there before, then I'd check all the accessories that are affected, make sure that the belt is on correctly.

Sounds like a case of "piston slap". My Jeep does that once in a while.

what about the rocker arms is it possible any of them were affected with the work you did?

i thinks its a coincidence about the idler pulley. but what exactly is piston slap?

Two things:
Piston slap and cracked exhaust header.
Both are common and go away when hot with no harm done. Exhaust is fixable but rather hard to do (and expensive). Crack is in area under the intake where the two pipes go into one before the flange.

If it is rocker noise, you can hear it under the valve cover.

if it is a rocker related noise, then i should definatel try to fix it ASAP right? but if its just piston slap or a cracked header, im in no real hurry, right?

First...find out what it is...
I use to use a stethescope or a screwdrive to pin point the noise...especially the rocker.

Stick your ear to a screwdriver...a long one ...like 36 inches ...and listen for noise in certain areas. Or get a steth...give me the correct spelling if you can.

The exhaust crack is documented and piston slap...i'll let others tell you about it...it is common.