Why does my 1996 Kia Sephia idle rough and spirt while stopped at a light. Replaced the master flow sensor and still does it. Has new spark plugs, new rotor bug, new distributor cap, new gasket inside distributor cap also, new catalytic converter too. My Kia when stopped runs rough and acts like it is going to stall. When I get the car up to about 15mph it runs great.