don't mess with timing...
if the idle screw had never been touched. DON'T TOUCH IT!
you could tell if there is a wax seal over the head of the screw.

best thing to do is clean the tb out...
and then... reset the ecu in any of the assortment of ways to do it ie. disconnect ecu...
THEN... turn on car without touching gas or brake pedal and wait till the rad fan cycle 2 times...

ORRRR

check for vac leaks...