I have a 2007 Kia Spectra5. Car has been surging when coasting in neutral for close to a year. Mostly 1400 to 2200 rpms. Rhythmic, up, down, up, down. Only after the engine has reached operating temperature. If you coast in neutral before that, the revs drop right down to 750 like they should. When warm, proper idle would settle at 750 rpm after car has come to a stop. Figured there was a problem with the IAC as I had cleaned earlier I thought possibly some sensor kleen had gotten into the motor and buggered it. Replaced IAC and gasket. Didn’t help. There weren't any vacuum leaks and the throttle body was cleaned. Replaced upstream oxygen sensor, throttle position sensor, thermostat and engine coolant temperature sensor. Cleaned MAF sensor. As the car only surged in neutral while coasting and stopped surging once I had come to a stop, I was wondering if it could be speed sensor related. So, along with the TPS, I replaced the VSS. Also bought a new radiator cap. Burped the rad and used new cap. Took throttle body out and cleaned again. After engine is warm, can stop the surging when coasting in neutral by turning on the air conditioning. Could this be a problem with the ecu?