Same post under right topics now. 
After 140000 miles I started to notice strange moments for my Roadmaster '96.LTD. .It feels like engine there is engine miss .When it happened first I just thought I hit some small bump on the road but then after several months those miss moments appeared more often.They are very irregular.Sometimes more often but sometimes only a couple times every mile driven. Can only notice them when driving at the constant speed over 50 mph. And sometimes when stopping for red light with your foot on the brake. I replaced spark plug wires but that didn’t change anything.
Any ideas ?
Sorry about my clumsy english 