Mercury Villager has 128000 miles. I have had distributor replaced, spark plugs replaced (expensive ones), throttle body cleaned, vacum leak sealed (reconnected), air filter replaced. When I am at a stop and engine is running, it has a rough idle, almost like a "shudder". It does not act like it is going to die or cut-off. When I put the gear in park it does not do this. Shifts gears fine (transmission is smooth), very good gas mileage. Only the slightest of hesitation when pressing on the gas from a stopped position.