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.

 

Best advice, take a video and post it up. That will help us better diagnose your problem.

 

That is normal? Every car starts high then ends low on a cold start up. After it is all warmed up what does it idle at?

 

after its done "warming up" it idles at about 1k rpm which is normal. The "not so normal" part is when it first starts up at over 2k rpm for about a good 10 seconds or so. i'll see if i can take a video of it tomorrow and post it

 

Thats not normal. Idle should be steady at 650 at normal operating temps. Cleaned your throttle body or anything lately? Look up the pedal method for idle reset and give it a shot.

 

Well it idles about 800 after it's warmed up. I just rounded it up a little. It's just weird that it starts up and idles for a minute at such high revs

 

Sound normal my g does that all the time

(edit: cold started my car eariler and it started at 900 then after warm up it stays at around 600)

 

I know it should be high on cold starts at first..

 

Best advice....^....even if it were freezing cold, idle should not be 2K rpm at startup and warm idle s/b 650 maximum. (normal) SEARCH idle reset and complete!
Gary

 

Mine always shoots up to around 2k when I first start it in the morning regardless of the temperature outside. After I let it warm up for a minute or two, it idles below 1k.

 

Mine did that too I have 5AT and when I put it on drive it used to start kinda aggressively so what I did was with my leg I just pulled the gas pedal toward me n it goes back to the normal rpm