98 monte carlo engine code

hello i am new to this today i have a little problem. i have a 1998 chevy monte carlo 3.1 and i have an engine code po440 and i changed the gas cap and reset it but it came back on. Does anybody have an idea what else might it be? if so i would be thankful for your information. Thanks david!

hello i am new to this today i have a little problem. i have a 1998 chevy monte carlo 3.1 and i have an engine code po440 and i changed the gas cap and reset it but it came back on. Does anybody have an idea what else might it be? if so i would be thankful for your information. Thanks david!

take plastic cover off of the inake manifold and check all vacuum lines esp. the ones going to from vent solenoid and cannister if all that is good check gas tank for leaks then replace the vent solenoid could be plugged or not working properly... if tank has vacuum sucking sound when you remove gas cap tank has no leaks..too much vacuum or not enough vacuum will cause this code.......