what can cause a rough idol? had a tune up at 100,000 now 130,000 on 1999 Mercury Villager

It idols rough when it is gear when stopped at red light or waiting in traffic. No check engine lights on

Asked by for the 1999 Mercury Villager
Rough idle can be caused by basic ignition tune up items (plugs, wires, cap, rotor...), or even EGR flow issues. Not to mention fuel injectors. Your "tune up" - what did it include?
plugs,wires cap ,rotor about 2 yrs ago. 1 fuel injector over the summer
You could have another injector. You could have an ignition system issue again. Only way to tell anything is to have a diagnostic tool hooked up to check specific components...can help.