96 LSI revving engine when in neutral

This a "come and go problem". My 96 Metro LSI starts to rev the engine to around 1500 RPM when shifting to neutral where it's supposed to drop to about 750 RPM when warm and at operating temps. Is this a sticking throttle cable case? or something else?
Thanks

First things to check with a high idle are:

1. vacuum leak, are all the hoses conected per the diagram under the hood?
Are any of the hoses cracked? A bad TB gasket will also alow to much
air into the compbustion chamber.

2. A bad idle control vavle or solinoid allowing to much air into the intake.
Check the same diagram to find the location of your valve.

Start with those two thing first. Also make sure your car is timed properly.