Unusually High Idle Flare

I performed a search for this problem but did not come up with anything.

I have a ’98 Forester S, 2.5, automatic, 146,500 miles, that has been doing something for quite a while that should probably be corrected, if possible.

When I start the vehicle for the first time on any given day, no matter what the outside temperature, it starts fine and the idle flares up to between 1500 and 1800 rpm’s and then almost immediately settles in around 1600 and slowly goes down as the engine warms up. It never stalls. I consider this normal.

The rest of the day, any other time that I start the vehicle, it flares up to as much as 2200 rpm’s when it starts. It almost immediately settles down. I consider this a bit high and am curious as to what would cause it.

The next morning it will start and not exceed the 1800-rpm’s previously noted.

This Forester has never experienced surging of any kind while idling or moving.

My Forester has been doing this for about two years now. Has anyone on this forum experienced this?

Thanks in advance for any help.