poor gas mileage on 2002 Saturn SL1

over the last couple of months the gas mileage has dropped tremondously and the engine is shaking like there is a screw missing. It stalls occasionally but hasn't done it in a couple of months

Asked by for the 2002 Saturn SL1
soundsd like it is running on 3 cylinders. that alone will give you lousy mileage. get it checked by a shop for tune up parts and why it is missing.