1991 Honda Accord wierd idle, fast idle valve?

For about a year my 1991 Honda accord with 230K miles on has a wierd idle only when warming up. It is does not always consistently happen. When warming up, instead of starting at 2000rpm then gradually dropping to 700rpm, when it gets down to about 1800rpm, it will suddenly just drop to 800rpm and back up again, real quickly back and forth. Once it warms up, the car is fine, but I know this is not good for the car. My first guess, was that the fast idle valve was getting bad info from the temp sensor, so I changed it, but it still does it. Should I change the fast idle valve itself, or could it be something else? I have heard there are others part that could be bad (solenoid, air intake valve, etc) Also, when warming up, if I turn the steering wheel, the idle jumps a lil, is that normal, or is the power-steering pump wearing out or something (i have no problems steering, and no leaks with power-sterring fluid). Thanks