Success at last. I cleaned the throttle body with MAF cleaner. At first Glance at the throttle body it was almost pitch black inside. I figured out that there should be a small 1/2mm Gap at the ends of the throttle circle itself and when Carbon Blocks that tiny gap - the car had difficulty being at idle- therefore it will be more prone to stall out. Now, THIS is key! . I DID NOT disconnect my throttle body from the sensor connector - Therefore I did not have to do any of the RELEARN procedures! After cleaning the Throttle body and bolting it back onto the intake manifold - I started the g35 up and . It was Puuurrrrfect! I also cleaned a little inside the Intake manifold itself due to it being very dirty at the inlet...

 

^

 

I just started to have this problem yesterday evening...exactly the same situation...on ignition starting the car...it either will die out or idle under 1000rpm...and thats when i had the car running for a long time...woke up this morning started the G up and no problem...so im cleaning out the TB this weekend...I have to say the forum really helps out a lot...thanks alot guys! oh, btw...where do you get MAF cleaner...??

 

Please do not use MAF cleaner for your TB. Use TB cleaner, it will do a better job of cleaning the carbon deposits.

 

I just use engine degreaser, not sure if its safe to use for that but it worked well.

 

For those of you having this problem:

I had a very similar problem after replacing my battery.

On cold starts, it would start up fine. But, on hot starts (i.e. after driving, shutting the car down, and then starting again a short time later) the RPMs would go up and then just gradually drop to zero.

My mechanic did an idle re-learn and the car was perfect.

Good luck

 

dont mean to be a noob but whats an idle re-learn and how do you do it?

 

So question mines is doing the same i legit changed everything and still stalls out any ideas?

 

https://lmgtfy.com/?q=g35+idle+relearn