i'm 19 and my 91"gxl" is my only car. i don't know if i could write three pages of problems about my car, just that it has idle issues. check your connections, too.
my car mysteriously died one night, all electrical was shut off. i never truly found the problem, but i fixed the terminals, cleaned them, greased them, and sprayed a lil wd40 on em. i also added a few extra ground straps; neg batt terminal to engine, neg batt terminal to chassis. i haven't had this strange problem since.
so, when and if you volt test, do it at the terminals and at the clamps. even then you don't have a for sure definate answer, so checking and thoroughly cleaning and tightening your clamps and terminals can be a must.

 

good tip thanks a lot...the reason i said this is my only car is because people list like 5 cars in theirs sigs and i got 1, so if something happens to one of them they can just drive the other one, i can't thats why this is so important, to me anyway

 

A faulty power door lock relay will kill the battery completely in about 2 days. Easy to check just by unplugging the relay and see if it cures the problem.