First start up of the day is fine. After its been driven, sometimes it wont start unless I pump the gas pedal while turning the key. Car runs fine, but sometimes while stopped at a red light it stumbles like it wants to turn off and sometimes it does. When it occurs too much, I spray the throtle body intake and it seems to do the trick but only for a few days. I've changed fuel & air filters, spark plugs & wires, O2 sensor, cleaned fuel injectors, egr & pvc valve. Fuel pump makes its electrical hizzing sound when key is turned so i take it its working fine. I havent learned how to check for vaccuum leaks. Repair shops dont mention the minor possibilities, they right away suggest the most expensive repair, fuel pump.