system too lean 03 gt

[StockGt03]

I have a code reader and it said the system is running lean. So I changed pcv, nothing. But changing the fuel filter help a lot and the light just came on in over three weeks. I don't know how to check fuel trim. Any ideas or experience on this.

[WolvesSoulZ]

Check for vacuum leaks.

[StockGt03]

I did I didn't see any of them loose or feel the leaking. But I don't get why the light would go off n take three weeks to come back on

[FordMan77]

With the car running, spray brake/carb cleaner around all the vacuum fittings. If you find one that makes the rpms rise or studder then that is a vac leak. When you replaced the PCV did you put both o-rings on it? There should be one around the PCV itself and a larger one that sits on the UIM under the cap.

Beyond that I've had my EGR cause this code as well. Could be stuck or the metal pipes leaking (you usually can't see the crack in the metal pipes unless you remove them).