I have a 1993 Buick Century with 3.3L V6. Runs fine and gets great gas mileage (27mpg). However, it has idled rough as long as I have had it. I have had the fuel injectors cleaned twice in the last year, which helped only slightly. I have also taken it to 2 different Buick dealers who have told me that the 3.3L engine just idles rough, and there is really nothing that can be done about it.
It's hard for me to believe that rough idle is normal for a mid-size luxury car. Does anyone have any additional information?