1998 windstar evap

code po446-evap vent . dont have manual, is there a vent valve/sensor on top of gas tank? my daughters van, would like to help her out. please help thanks ray-how to troubleshoot, also codep1452, or p1457 came up-unable to pull fuel tank vacuum/ or unable to bleed up fuel tank vacuum. po446 is evap emission control syst.vent control circuit malfunction

I am not familiar with that code....but I do know that you will get a similar code if the gas cap is not sealing correctly. I do not know the excact code. A locking gas cap usually leaks air....or if the gas cap is not on correctly.
The code (and light) will stay for a certain number of cycles after the problem is corrected.
I would try this cheap and easy first.

The vaccum source for the charcoal canister (for gas tank vapor recovery) comes off the PCV vaccum line. There is a vapor purge solonoid mounted on the firewall...kind of behind the throttle body. The PCM sends a signal to the soloniod....and that turns on the vaccum to the vapor recovery. There is another, identical looking solonoid, that is mounted on the back side of the upper intake manifold.....which gets its vaccum from the PCV line also.... That is the EGR vaccum solonoid...which provides the vaccum to open the EGR valve. On our, '96-'98 years.....the PCV valve and these connections in the PCV line are all back in behind the upper intake manifold.....so they are hard to see. If you have any vaccum leak in there...you will hear a loud hiss.