idle problems

K this is a stumper. When i run my car for about 15 minutes to 1/2 hour. All of the sudden it start iddling up and down like crazy. It idles up to about 2500RPM then sounds like its going to stall but then goes back up to 2500RPM. it does this until i get in the car and pull up on the gas pedal.... And should the car rev up when u lift the cable going across above the valve cover?

my car does this too after about 10 mins of idle the rpms jump up and down, it sounds like its gonna stall then goes back to normal, i dunno what rpms im hitting cause i dont have a tach heh...Just lettin u know your not the only one! sorry couldnt help

its you canadians :p

my car was made in canada, sold in the US and i brought it back home :), its all in this wierd ass mph stuff heh