I have a 97 chevy malibu which is idling too high, when I switch to drive or reverse in jumps or bangs but drives fine ? what could be the problem ? I replace the pts sensor and it became worse ( the idling )

The ( iac ) idle air control needs cleaned. it is mounted on throttle body to control idle speed, remove the torx screws holding it on. do not put body of valve in any liquid or it will ruin it. clean valve on end with carb, or throttle body cleaner. use a old tooth brush to clean it, or similar. this should do the trick if it is not bad!! also check wiring to it for broken wires etc. have a good day !! do not push on valve or it will mess up setting. proper setting is 1 and 1/8 from tip of valve to body of iac. hope this helps.