Sometimes when i start my engine for the first time of the day it revs to about 2500-2800 and then slowly comes down...anyone elses car do this?

 

Exactly the same!

 

Its common on all of the Porsche's 911, Boxster, Cayman etc, I noticed that other cars such as Mercedes-Benz or Jaguar take slightly less time to get warm.

 

my old Lincoln used to do the same...

 

The engine management system is programming for cold starts, (programmed in all aspects), since the motor is cold and its not up to running temperature the fuel isn't being burned that efficiently yet, in order to keep it running the EMS compensates by making the fuel mixture significantly richer, how rich? Well that all depends on the model of the car and how the cold start was programmed. Also someone can correct me if I'm wrong but the throttle is opened at a slightly higher percentage as well. Also a benefit of the car being so rich during start is that it warms up the engine quicker as opposed to having a normal a/f ratio (being leaner).

*Disclaimer* this is what I've come to understand and read, I could be wrong its been a while since I've read the book.

 

soime of my other cars do this but do not rev nearly as high....

 

Every motor is different.

 

I think part of the noise may also be the air injection pump which helps light up the cats to efficiency

 

I have heard it heats the cats; once the rpm drops .. your good to go.

 

My car did this only once, in 6 mos. of ownership, most of which was in relatively cold weather. I don't think it's a problem unless it happens during the warmer months.