Drive for 12 miles and Loose power going up hill on 1998 Ford Windstar

After drive for 12 miles get to up hill and loose power and front catalytic converter on the front turns red

Asked by for the 1998 Ford Windstar
No power loss at say 4 mlles? Light on? Any engine work lately like maybe crank angle sensor that would affect timing? If cat. were restricted should do it from the start! Let a mechanic check it out!!