1999 Ford Taurus problem idling

I have a problem starting the car after its been standing for more than 8 hours in a hot or slightly cold weather. It starts ok and stops immediately. Starts again but have to control the idle speed by the accelerating pedal. After about 30 seconds the idle speed is normal and car runs very smoothly. It has new spark plugs, new ignition wires, new fuel filter.
and new air filter. Engine check light once came on indicating egr valve code, but now check light does not comes on and the problem seems to be getting worse. I need to fix this problem and answers appreciated.