Vacuum leak(s). Bad idle stabilizer valve (ISV) if the injection system is CIS-E. You might also check/replace the ECU temp sensor if it is CIS-E. It is a white sensor on the bottom of the upper radiator hose flange -- You need a multimeter to check it -- the resistance varies with engine coolant temp.
Check the air intake tube carefully for rips and tears. FR
Modified by Fat Rabbit at 8:19 AM 2-4-2009