i really hve no idea what is wrong with my evap system, yea i know i bring this up alot but ive been thinking, theres got to be a manual purge valve on the system somewhere right? and if i disconnect my battery for long enough will it run the system through all the tests again? i was just curious because it seemed fine until temps got below 40 degrees thas when it really started acting up so i dont wanna cut into my car (gas tank) to no avail

 

First thing is to see that you have the proper gas cap and that it seals good. What symptoms are you getting? Usually the EVAP does not affect how the engine runs except smelling like gas, and setting off the check engine lite. There is no manual valve, but there is one controlled by the computer.

 

I have seen a tank not venting cause a poor running condition. I have also seen one implode! (a bmw had a problem with a solenoid) Plus you could do as little as to leave your fuel cap off and it will show a code on OBDII.

 

that was actually the first thing i replaced, was the gas cap, although the one i replaced was cracked entirely and was holding no seal whatsoever, but i bought it with that....i got i think one tank of gass without trouble, because less than a week after i purchased it the check engine light came on

 

The code could have been cleared before you purchased it and in some cases it could take a while for it to come back until a proper drive cycle is done.