Damn! I used the wrong word.

 

Ha! That is exactly what it is! So do I have to replace the evaporative canister too? What have we done to the truck driving it like this? Thanks again! You guys are lifesavers!

 

no you don't need to replace the evap canister. its just a can of charcoal and air.
you can get the purge solenoid at autozone for about 40 bucks for an 01.
http://www.autozone.com/autozone/par...mString=search


you haven't hurt anything. the purge solenoid opens a valve which allows engine vacuum to pull vapors from the evap canister. it also monitors the pressure somehow. i don't know what the knocking would be, maybe the engine vac is rattling the valve back and forth or something.