ok i have a 1990 buick lesabre and about 3 weeks ago, it started it started idling kinda weird, it only happens when im in Park, when i put it in gear to drive it drives beautifully. Also if im at a stop sight or red light when i take off it stutters a time or two before it finally takes off. and thats only when i make a completely stop. if its a rolling stop (which how many of us dont make em lol) it will take off fine without stuttering. now around the time this first happened a spark plug wire came loose and was sliced by the fan. i temporarily replaced it with a wire that my dad had taken off his oldsmobile 86 when he changed his plugs, until i change the plugs on mine, which hopefully ill do this week. So could the problem be that wire that came from my dads car or something else? i recently changed the o2 sensor,
rough idle on 1990 Buick LeSabre
I've had the same exact problem with my 1990 lesabre and i found out my idle air control vale (IAC) was not working correctly, that is after i was told my egr vale was bad LOL ($10 at my local friendly neighborhood junk yard) . I also had a bad coil in my coil pack. I was strapped for cash at the time and went to the junk yard and got the coil pack,module and IAC for $35 and my car runs perfect now and that was a year and a half ago! Good Luck!!!
If you've changed the spark plugs and spark plug wires and there's no oil on them upon inspection, then you probably have a burnt valve. Have your mechanic do a compression test on all your cylinders and whichever one reads lower that the other's will have the bad valve and you'll need a valve job.