Can you get a video recording of what this is doing? Does this only happen when in park?
Clearly seeing this will help confirm what is happening because when you say it is slow to return to idle
So, the things that will cause a high idle/ RPM are normally fuel and air that is not getting cut off.
So, if we have a vacuum leak or a leaking injector then we will have a slow return after you give it more throttle.
Here are a couple of guides that help with this:
We should check the fuel pressure when we go to key on and see if it holds for at least a few minutes.
Then we should check the fuel pressure while it is running and slow to return to idle.
Let's start with this info but if you can get a video of what this is doing then that will help with getting us on the same page of this issue.
Tuesday, March 1st, 2022 AT 4:32 PM