high idle when warm...any ideas??

[sunjayz28]

This started happening recently, and happens only after driving around for a while. The car idles at around 2000-2200 rpms. When i'm driving, and shift into neutral, the rpms rise to around 2000-2200 range, and they're back down after a little while. My SES light is on due to a bad cat--could this cause the high-idle problem?

Its a stock 96 z28.

[Predator86]

I had the same issue with my car and it was a vacuum leak but im carbureted so i doubt u have the same problem.

And no i don't believe a bad cat could alter the idle.