This past week we had been experiencing low to high idle.I reset the computer by unhooking the battery, plus I used fuel system cleaner in case there was a problem there.The idle did smooth out but not 100%.The IAC (Idle air control)had been replaced last year when engine (v6) was having the same problem. Initial diagnosis was the IAC again. Dealer replaced the IAC and the throttle air valve assembly and gasket for free including labour, but problem still persisted. Cause was found to be the upper intake gaskets (part # F5RZ 9H486)and we are now back to a smooth 750 RPM normal idle.
I hope this feedback may help others with the same symptons.
