Hiya, welcome to the Forums.....

Does this happen when the engine is cold during the warming up process?

Totally normal.

 

Yes after it’s been sitting all night

 

Every EFI engine controls air, fuel and idle rpm automatically for efficiency and emissions control. If you remained in park as the engine warmed up, you noticed how the high idle lowers without touching the gas pedal. That's all engine programming to account for ambient air and engine temps. It's not necessary to wait for the engine to warmup, returning to normal idle rpm and simply wastes fuel. Cold engines requires extra fuel on startup along with higher idle rpm otherwise the engine stalls and dies. As coolant begins to warm up, less fuel is needed and rpm lowers automatically.

It's better to startup, let engine (high idle) run from a few seconds (warm temps) or more (cold temps), then drive a few blocks at low to moderate speeds. Engine loads from driving will warm the engine faster than sitting in place and does not harm the engine or xmission.

 

https://www.subaruxvforum.com/threads/high-revs-on-start-up.190799/#replies

https://www.subaruxvforum.com/threads/high-idle-on-cold-start-when-it-is-safe-to-put-the-car-into-gear-and-drive.186967/?post_id=2174811#post-2174811

 

A rich fuel mixture is needed and higher idling RPM until the temperature of the motor rises internally. Perfectly OK. If it's doing that when it's 90 degrees outside, see your dealer.

 

Yeah, the time for RPMs to come down should vary based on ambient outside temperature, and the current engine temperature before starting.

 

Depending on ambient temp, if you put the car in Neutral a minute or so after starting that will bring the revs down, at which point there will be less driveline shock when shifting to R or D

 

What is a cross track?

 

Yeah, the time for RPMs to come down should vary based on ambient outside temperature, and the current engine temperature before starting.

What is a cross track?

a car