Hey all. I have this problem recently. I searched and found some ppl had the same problem before but I cannot find any one actually answered this.

my '8 used to start with 700-800 rpm with A/C on, weather = 100F. then fall comes and weather became cooler (60-70F), then I started the car without A/C on, it usually rev up to 3000 rpm, and goes back VERY SLOWLY to 700 or 750 rpm at P, constantly!
(it takes few seconds to drop to 1-1.5k and take few minutes to drop from 1k to 750)

Sometimes it will also drops to 660, tho- in most cases still around 750.

I feel slight vibrations on the seat when at P. probably a little stronger than hot weather, or maybe just psychological effect.

So, how would you diagnose this? would you suggest this is the rough idle?


Thanks a lot

 

At P? Do you mean when the car is in park?

It's completely based on temperature... I'm sure if you search around, you can find some information on it. Most people would recommend not driving the car around until it settles at a normal idle speed... others will recommend that you wait till it completely warms up. This is normal and not something to worry about.

 

just wait til it gets colder. Your rpm needle will jump all over the place!

 

If so, that would not be a normal running condition....