98 3.8 Windstar bucking and rough idle

The van has 64,000km on it and over the last 2-3 months I notice that it's idling a little rough at times and it also bucks at low driving speed say in a parking lot. What the heck would cause this??

Also the "CEL" doesn't come on, so I'm not getting any codes. BTW are the stock plug platinum??

Thanks,
Anthony

Check out the coil pack...Just replace mine. when it starts to go out the check engine light will blink other than that you may not get a light..