car stalling out

1991 BUICK LESABRE
142,000 MILES • 6 CYL • FWD • AUTOMATIC
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RANCHERHONDA
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1991 buick lesabre 3.8 auto,144000 miles.after car warms up it starts bucking,usually a few times then straightens out.it is getting worse now sometimes even stopping engine.I put in neutral and it starts right back up.I have taken to mechanic and he says no codes are thrown.He put a used module and coil pack in.Didnt help.He then put in new cam and crank sensor.Didnt help.He now suspects bad ground or bad computer.I havent gone back as it is getting pricey guessing like this.Any help would be so much appreciated.Thank you in advance
Mar 20, 2011 at 3:18 PM
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JDL
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Does it do this only at idle? Will it act up in park in your drive-way?
Mar 20, 2011 at 4:03 PM
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RANCHERHONDA
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it starts acting up after 10 to 20 miles at any speed from 10 to 75 mph
Mar 20, 2011 at 4:08 PM
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RANCHERHONDA
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idles fine only acts up while going down highway.before it acts up it seems to shift back and forth constantly and my mechanic says this is because engine isnt runnig properly and computer is telling it to shift
Mar 20, 2011 at 4:11 PM
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JDL
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Did you try a test drive with tranny in drive instead of over-drive,any difference?
Mar 20, 2011 at 4:18 PM
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RANCHERHONDA
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yes ive tried just in drive,also with cruise turned off.all accys off nothing seems to help.
Mar 20, 2011 at 4:27 PM
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JDL
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I wondered about your vss/vehicle speed sensor. Your mechanic probably already considered that. I know you don't want to throw parts at it. Without something more to point us in the right direction, I don't know.
Mar 20, 2011 at 4:40 PM
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