rough idle on 1990 Buick LeSabre

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,

Asked by for the 1990 Buick LeSabre
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.
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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!!!