Engine loses idle speed control. with no throttle applied by driver the engine will race to 2500 rpm, then back to 1000rpm, then back to 2500rpm and so on. sometimes settles at high idle, 1300-1500rpm steady (correct idle is 700rpm or 750rpm i think). vehicle will surge with no throttle applied when this is happening. will happen with vehicle in motion or at stoplight. sometimes cycling ignition off/on will correct problem, sometimes not. two events this occurred after about 20 min driving, one event it occurred immediately after cold start. always gone at next cold start (after several hours soak). no obd code is stored during these events, (pending or otherwise) despite idle speed far being out of commanded specification. issue has occurred three times, first time was 11/10/17, most recent 04/24/18. have video showing engine speed racing 1000-2500 rpm with foot off throttle, can provide if needed.