Have an air leak, where to look for it?

found out my check gas cap light came on because theres an air leak, so where do i look for it thanks.its a 2002 4cyl.

I'd start at the hose nipple under the throttle body. There is a small diameter hose that hooks up there, goes thru a small valve and flow sensor on to the carbon cannister. From the cannister, another hose picks up and goes to the firewall where it hooks to a metal tube ... and from there back to the fuel tank.

Most likely, the leaks are in the hoses under the hood ... but if not there, you will have to check the hoses on top of the tank.

actually there is a design flaw with the fill tube from the gassnozzle to the tank. they tend to crack with age. i dont know exact process but i have seen a fix that envolves a fuel resistant rubber hose to replace it. or a ford factory replacement. i would start by checking the actual cap first

i'll check under the hood, because when its on i can hear a noise like a leak in the engine bay.

i'll check under the hood, because when its on i can hear a noise like a leak in the engine bay.
ok???

turns out there is an air leak in the bay and i've found it but its a small white plastic hose about 1/4 inch in diameter that goes to another little hose and into the carb housing is that it?

or should i replace the gas cap?

Just continue to find and repair air leaks. When the system is leakproof enough, the light will go out ... that is, after a 100 miles, or so, of driving.

And, yes, the gas cap may be part of the leakage.