1995 lumina 3.1. In the morning when I first start the car the idle is high 2200+ rpm. Also when it is idling high like this ifI rev it to 4000rpm or so it starts to cut out and misfire when in park-neutral. The car has a slight hesitation when it is acting like this. I live in Chicago and it seems when it is really cold the car runs better. Any ideas?

Thanks

 

High idle could be a vacuum leak, the cuts off at 4000 rpm is the fuel cut off from the pcm