I have a 2000 ford f150. recently the truck quit holding an idle. the engine turns over but as soon as I let off the gas it dies. No sputter or anything just turns off. I took it to auto zone and had them hook it up and was told to replace the O2 sensor which I did and that didn't help. Any suggestions would be great! Thanks

bad iac motor, replace and it will be fine. the iac ( idle air controller ) motor holds the throttle body open and adjusts for weather conditions and a/c and such. they are not that expensive.