Once in a while my 08 IS250 will scream at 3K RPM when I start it. Doesn't have to be a cold start, could happen after the car is already warmed up. If I "blip" the gas pedal it drops down to normal. Guess that's a habit I have from the old carburetor days.....anyway doesn't happen that often but am wondering if others have had this happen and what controls the RPM at start. 98K miles, otherwise runs great!
Thanks, Mike

 

Brake cleaner/starter fluid "trick" for locating a possible vacuum leak somewhere?

 

This used to happen on my Acura RSX. I ended up having to replace my throttle positioning sensor but I'm not sure if that will fix the issue on an IS

 

I'd clean the MAF sensor, check for vacuum leaks, and maybe pull the accordion hose of the intake and inspect the throttle body for buildup and debris that could cause sticking. That said, if the ECU detected stalled motion you'd have a CEL for that.

Next in line is to check the coolant system and coolant sensor. If it's not reading right the computer may do strange things.