When I initially start my car it idle's high for a long time
Takes a while to settle down

 

Need alot more info then this. I have a question, or 6. How high does it idle? How long does it take til it kicks down? Any noises that go along with it? Could just be a vacuum hose cracked. (you might hear the suction) What year is the car? How many miles? Any recent work done? We need more info.

 

Starting out over 1000 to 1200 RPM is normal in park for a couple minutes.Should settle down into 600-700 range pretty much after,it varies.Settles down quickly as you drive it.

 

You don't define a "long time"... but mine does the same and then settles down after it warms up. Don't think I'd worry about it unless it's a real high idle. That would be out of the ordinary.

 

Failed thermostat, see:

https://www.clublexus.com/forums/ls-...hermostat.html

low coolant level, improper % coolant mix or temperature sensor.

If original.thermostat and coolant sensor then replace both.

Use OEM parts...more expensive but no issues.