Got a 99 F450 7.3 with 190k miles, started acting sluggish. When cold, it wouldn't stay running, almost as if out of fuel. Would stall out when you pressed and released the accelerator but would idle fine. Now, it won't even stay running. Still acts like it's out of fuel. Changed the air filter, fuel filter, and added injector cleaner and conditioner. What else could it be? after warming up when shifting gears and letting off throttle it stalls and when restarted lets off blueish white smoke.

 

Welcome to FTE, dann167.

Fuel pump or Idle Air Control (IAC) valve are 2 possibilities that come to mind.

 

i changed the fuel pump and filter cleaned the tank out got it to run but once the rpm hit about 2200 the truck would start acting up and i would have to let off the throttle