What causes a clunking noise when decelerating? The car also goes by itself. on 2002 Ford Taurus

considering buying this for my sister but don't want any major problems

Also, could the idle be set too high? When you take your foot off the gas, the car still keeps going instead of slowing down.

Asked by for the 2002 Ford Taurus
you could have a tps problem take to a shop and have scan tested