[xxxBlakexxx]

Do you seriously mean 50 -100 rpms? Anyway, you definately have an IAC problem. But also, your base idle could be set too low.

Here is what you need to do:

1 - Start the car.

2 - Open the hood and unplug the wire harness that goes to the IAC. When you do this, the car shout NOT die. It should almost die, but NOT die. If it runs too smoothly, then the base idle is set too high. If it dies, then the base idle is set too low. If it dies, adjust the idle set screw on the throttle body in order to open the butterfly just a tad. Then restart the car to check the setting again. Keep making adjustments until it's right. (your SES will come on btw). If you don't need to do anything, then don't wory about it.

3 - Remove the IAC and claen it with some intake cleaner that is labled for throttle bodies. Soak it good. You can't damage anything. If that does not work, replace the IAC.

Let me know how you make out.

PS - you need to clear the SES