My 2000 Accord with F23A1 engine blew a head gasket at 283,000 miles. I had the head checked for cracks, pressure tested, and milled to make sure its flat then put it back together with a Felpro head gasket. Now all seemed well until the engine warmed up and the idle speed jumped to about 2k. I shut it off and let it cool, checked the coolant and started it again...it idled great until it warmed up again. I drove it a few miles to see if it would clear up and it runs ok under a load but will sputter when I lift off the throttle and feels a bit sluggish. After the test drive it idles about 1200 to 1500 when in gear but stays steady somewhat steady. In park it surges rapidly from 800 to about 1200 rpm. I have not removed the IACV yet but wondered if that's the next step. A Honda mechanic thought it might just be air in the coolant lines but thought that would go away after driving a few miles. Suggestions?