Hey, I have a 2005 G35 coupe 6mt with about 60,000 miles on it. I've noticed this for a while now but my car tends to start up at a really high rev but then will slowly lower the idle rpm after a couple minutes (from over 2k+ rpm to about 1.2k or so)(I've seen as high as an initial 2.8k rpm but shortly afterwards idling at 2k and lower). It just seems really strange that it does this not only when its cold outside, but even when its hot outside. This only tends to happen when I haven't used the car for lets say more than 6 hours. Does anyone know what might be wrong with it?
It's also tough to show the people at the dealership because by the time I reach the dealership, the engine will be warmed up and it doesn't do it anymore. It only does it when I haven't used the car in a while.