Hello,
I recently bought a new 2008 RDX Tech, but noticed especially first start of the day in the morning after starting the car, when left in park the car idles a bit rough (but maybe that is normal, as thereafter all is fine).

 

I noticed similar, but rather in drive and stopped at a red light shortly after only just starting the RDX. I think it's normal. I mean, it's not significant but slightly noticable. A 4-cylinder will never idea as smooth as a V6. I wouldn't worry about it unless you feel the engine is not responding properly.

 

Yes, an in-line 4 will idle a little rough, especially in cold weather. I would also imagine the turbo would have some effect too in cold weather. It's just the nature of the beast.

 

I noticed the same with mine and it does go away shortly after the initial start-up.

 

All cars do this but noticeable more on 4 bangers (especially if you are coming from a non 4 cyl vehicle)

ECU needs to warm the car up fast and this is how it does it. Idle rpm on a cold start should sit just at or bit less then 1500 RPM, once warm should be at 700 rpm.