Usually when a car wont iddle it may have a blown head gasket , remove oil filler cap on rocket or tappet cover check for creamy coloured oil , if so blown head gasket , also when morot is cool remove radiator cap and check fro brownish residue under cap if so blown head gasket .
remove each spark plug if one or more of them is white on tip of plug water is getting into cylinder ..

if none of these some carby's or throttle body's have iddle screww which can be adjusted to speed up iddle , or if throttle body it may have an iddle soleniod which may need to be replaced ,
i hope for you is is just and iddle issue , both the solenion and head gasket arnt cheap to fix.
the soliniod although easier to remove and replace its cost is usually .... expensive on most makes of cars , dont know why just because there greedy dealerships !

hope you need only to adjust carby or check timing is o.k

good luck hope this helps