Fuel injected cars don't have idle speed adjustment screws. The Engine Computer controls idle speed through the idle air control valve. That is a passage around the throttle blade. On many cars the computer will lose its memory if the battery is disconnected or run dead and will have to relearn "minimum throttle" before it will know when it has to be in control of idle speed. Until then you also will not get the nice idle flare-up to 1500 rpm when you start the engine, and it may be hard to start unless you hold the gas pedal down 1/4".
Some engines are also prone to that air passage becoming plugged with carbon. The injectors will spray more fuel but you won't get the needed air to go with it.
Not all cars need to do something special to relearn minimum throttle. The only ones I know how to do are Chryslers and those are simple. You need to drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals. You may need to find out your procedure from a Kia mechanic. You can try calling the dealership but often the guys behind the desk don't know the procedure.
Try decoking (cleaning) the throttle bore, here is a guide on how to do it, it will help
Wednesday, May 15th, 2013 AT 9:32 PM