Thanks for the detail Eljefino!
I just try the saturn. If I restart, the idle did come down, but still after driving a while, the same thing happen.
For the air intake tube, is the tube connect air filter?
Originally Posted By: eljefino
What happens if you turn the car off then start it again?
The newest saturns don't have coolant sensor issues like the old ones, but the throttle position sensors get flaky. A restart is effectively a reboot, which rezeroes the sensor at its new value.
The flaky sensor won't throw codes, usually. As part of its programming, if the car sees 1% throttle, it opens its idle speed control passage all the way for emissions/ dashpot duty.
If you want, take off the air intake tube. At 6 oclock on the throttle body you'll see the idle air bypass hole. Start the car and put your thumb over this hole. The car should almost stall or at least idle a lot lower. If you still have a high idle you have a vacuum leak somewhere.