Car feels like it is going to conk out while stopped

Hi,
I have a 1990 Ford Crown Victoria Wgn. 190,000 miles, v-8, 5.0L.
Upon stopping at a light, car has rough idle and then feels like it is going to conk out.
I put the diagnostic to it and at first it gave the code to change the egr sensor which I did. It still does the same thing. I tried cleaning the Idle Control valve and it helped a little then it starting again. I put the diagnostic to it again and now it states nothing wrong.
Would any one know what is making the car do this?
Any help would be greatly appreciated.
I cleaned my spark plugs which was changed last year, changed oil, air filter, oil filter, fuel filter, and also had a new fuel pump put in.
Thank you