if it's a fast surge in the idle, I'd first blame a vacuum leak. spray some carb cleaner or something similar around all the vacuum lines while it's idling. if it shoots up sky high, then bam, you found the hole, and you replace that length of vac line or fitting.
If the idle surge is slow, the first thing I'd blame is the IAC (idle air control)
burnsy...funny that you mention that, because the exact same engine came in Cavaliers and Malibus
