I have a 93f150 5.0 302 and i was wondering if anyone could tell me why that only on cold mornings when i start it up and walk away it sounds like someone literally is in the truck holding it to the floor. then itll let up and start doing it again. i cleaned out the throttle body and seafoamed it. i didnt change the fuel filter bc it only does it when in park. as soon as i shift into drive it idles fine. any ideaas?

 

first mistake was using seafoam. Idle air control valve is shot. replace it

 

and i just put seafoam in the vacuum line why is that a problem? and thanks for the iac answer