not sure what it could be. only at cold start my car's idle bounces at 1500 rpm for almost exactly 10 minutes then the thermostat opens and it idles down and runs perfect. i tried adjusting the tps but that didnt help its where it supposed to be and the ecu is shooting a iac sensor code but the car has always shot that even with the other motor i had. i put a good iac sensor on but it still idles bad. any ideas on what it could be? thanks