high RPM

Can any of you guys tell me all the things that would kick the rpms up to say 1000 and hold them there somtimes? I know that when the car is cold its starts there then warm it goes down to around 500 and thats good. But there are times that the rpm just likes to stay around 1000 or so.. Like if Im just getting off the freeway in mid day and the rpms stay at 1000?? Figure I must be loosing MPG cuz Im only getting 42.. Oh so I dont make a newbe mistake My Geo is a 95 metro, 1L, 5 speed, No AC.

Thanks for any info..

Could be a vacuum leak, but I'd bet the Idle Air Controller is going bad.

42 mpg is exactly what you should expect from this car. The 50 mpg Metro ended in 94.

Thanks, going to have to get my vacuum guage out of storage and check if thats the issue.

I do have a question about this (Idle Air Controller) Dont have a book on this little thing and cannot find it on autozone web site.

Is it one of those electromagnet looking things on the side of a carb (Old cars) that when voltage is on it, it moves a little rod to increase the RPM?

This is a feul injected car. Does the computer tell the engine to increase the RPM when the battery is low? Just cuz it seems that there is somthing strange with teh charging system...

It's bolted to the Throttle body and has water, vacuum, and electrical signals from the computer going to it. Uses all these things to adjust the idle by means of a diaphragm inside that is prone to breakage.