Purge valves are easily cleaned with WD40. I also squirt some in the hoses and let the vacuum suck it through the valve..
If the valve is funtioning , you can feel the frequency beats with the valve in your hand . They just get dirty from fuel emiisions and stick open/closed.
If stuck closed , they do not allow flow, but if they stick open, then they create an internal vac leak and will raise hell with fuel trims. Many an unfound vac leak is simply a stuck open purge valve..

They use a rapid on/off feature so the engine does not read lean/rich by gulping all the air at one cycle. It should come on after 70C.............