Help! I have an 88 CRX Si with the 1.6L 108 hp engine.

I had the erratic idle problem and it was mostly taken care of by burping the coolant system (Thanks to all the info on this site). With the erratic idle problem the car would go between 1000-2000rpm at idle. Now that seems to be gone BUT

every now and then, I'm sitting at idle and the rpm will go up to 3200 rpm or so and will stay there. After driving a little while longer it will return to a regular idle. It will happen only once on my 12 mile commute to work. Sometimes it will behave the entire time and have a low idle.

Any advice?