Is it the gas valve or the ifc.

Don`t know what a ifc is, but before you start replacing parts, try cleaning the flame senser real good with some fine steel wool or fine sandpaper, don`t cost anything,to give it a try

Let us know how it turns out

The ifc or integrated furnace control board. Answer to wmproops question.
The ruud silhouette gas furnace won't stay on to heat the house. The igniter lights up the pilot burner for a few seconds and then shuts off. However i am able to ignite the burners with a lighter. And they will burn until the thermostat is satisfied.