2000 gt idle control/revving by itself

I have a 2000 grand am gt 2 dr with 180k miles, car has been running great until recently. The car will be driving fine, then the engine will start accelerating by itself, usually going up to and staying at 1900 rpms. When I put the car in neutral, the rpms shoot up to 3500 and stay there.

Also, while the engine is revving itself and the car is in drive, pressing the gas will up the rpms and the car will not speed up until I press the gas further down, then the car responds.

I have had trouble finding information on this issue, and while I know the car has quite a few miles, any help on this would be appreciated. I have not minded having to switch between drive - neutral, but I'm sure it will get old quick.

Also, the temp gauge has occasionally been showing higher temperatures from the normal 200, it will go up to 215-230 on occasion. The coolant is fine and is not leaking.

The gas gauge also has problems, it will change drastically, going up and down, when I park the car. This hasn't been a problem, and while i think it is just the gas sloshing around when I park, it may be related to idle problem.

I just started to search the site for this problem, but any help is appreciated.

Any codes? Start with cleaning the iac sensor.