05 freestar lurching/missing
 

I have a 05 FreeStar. 105,000 miles. 4.2 6 cyl. Just replaced plugs and wires. Air filter is clean. When I'm on a highway and set my cruise, the van feels like it's missing/lurching at a constant speed. I have no issues when I accelerate, nice and smooth. Averaging 17.5 miles city/highway.