High Idle at Start

[ccozic]

I have a 1994 940 nonturbo automatic with 165K miles.

Lately at cold startup each morning, the idle shoots way up to 2K rpm on the tach. It takes a few minutes to come down to 1500.
After I've driven about 3-4 miles, the idle is about 900rpm at a stoplight.

At cold startup in the evening, it revs at 1500.

I have month-old NGK copper spark plugs in it. I can't remember if this idle problem existed before I changed the plugs.

Just wondering what is causing this. That high RPM can't be good for the motor when it's not warmed up correct?
The car has many newer parts I've installed: coil, 02 sensor, crank position sensor.

Would like to correct this, so thank you for any suggested fixes.