1995 Dodge Intrepid Intrepid won't start when cold.

Engine Performance problem
1995 Dodge Intrepid 6 cyl Front Wheel Drive Automatic

I have a 1995 Intrepid with a 3.3 liter engine. When the temperature outside drop below about 20 degrees F it just cranks and won't start. I thought at first it might be a fuel problem but it acts like it isn't firing. Once the outside temperature warms above 20 degrees or so the car starts and runs great. I read something about the 3.5 liter intrepids needing a hotter spark plug to fix this problem. Is this also true of the 3.3 liter engines? Has anyone run into this problem? I can't remember, but I think there might be platinum plugs in the car. Would changing back to the stock Champion copper plugs be better? Any thoughts?