Um, that would be because you have power steering.

 

every care i've ever driven in has had power steering and that has never happened before, but thanks for the wise *** answer. if someone could explain why this happens w/power steering, if that is in fact the reason, i'd appreciate it

 

I'd hate to see your reaction when I am being a smartass. I guess I just figured it would be obvious why that was the case.

I'll go into detail. Open up your hood and look on the left. The white tank at the back left is your power steering fluid. It should say as much on the lid. Follow the black hose at the bottom, it should be larger than the top one. It goes to your power steering pump. That pump is what circulates the fluid making it easier to steer. Follow the belt on the pump back to your engine. The engine drives the pump the pump moves the fluid.

So, when you are in idle and don't really need steering the engine isn't going to bother with the extra RPM's that the pump needs as a base to operate the power steering. Because driving that pump transfers into a more fuel being wasted. The same reason you will see the RPM's jump up when you first switch on the AC and the compressor starts being used. In the future we may see more cars using electronics for power steering rather than using the engine. This transfers to better fuel economy and more horsepower.

 

i knew it was because of the demand from the power steering... I just wanted to know if it was just my car. I had a 98 Chevy Nova with like 80 something HP and it had power steering... the rpms never jumped up though... and plus i have never seen that before. Even in my 2.0 jetta that never happened... interesting

 

The increase in RPM is a response to the increased demand on your engine when you use your power steering. Same deal with AC and added electrical load from the alternator. The bypass stepper motor controls an alternate rout for air into your engine independent of the throttle you control with the gas pedal. I think on your cars the ECU monitors your steering position sensor but may also use a pressure switch at the power steering pump.