If it starts up right away without having to cool down for a half hour, it might just be idling too slowly. You can prove that by holding the gas pedal down 1/4". That is typical after the battery has been disconnected or run dead. The Engine Computer has to relearn "minimum throttle" before it will know when it has to be in control of idle speed. To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the brake or gas pedals.