I just replaced my Alternator a week ago and the.

I just replaced my Alternator a week ago and the next day I began to have idling issues. When I start the car in park, the engine RPM drops low and idles rough for a couple seconds but then picks back up. This also happens occasionally when I come to a stop, and every time I put the car back in park. I was not having this issue before the alternator was replaced. There are no warning lights illuminated.