My first Contour V-6 had a similar problem early in ownership. Turned out to be the plug wires. Either they were bad, or I had two of them mis-routed. Double check the plug wire routing, then see if some fresh wires from a freindly CEGer near you will 'fix' the problem. Cost you near nothing to try...
Beyond that, also check/test the coil pack. I may have an extra if your mom needs it - I'll have to look.
