ive got a 2000 4.0 rig with about 88k on her and every now and again it makes a loud noise sounds like a sucking or kinda a blowing noise. at first i thought it was my train horns with a slow leak but its nots constant it comes and goes and when the truck is running. it makes the noise under idol and load. i think it might be a vacuum problem but i dont notice anything under the hood.. and like i said it comes and goes so its hard to isolate were exactly it is coming from. i did notice it does it more in the colder weather as its starting to warm up i am noticing it is happening less frequently. i have also noticed if it starts making the noise and i briefly hit the gas pedal hard it will stop. anyone know of what could be wrong or has had this happening on there rig. thanks guys for your help

 

it could actually be described as a loud humming noise i guess.. its tough to explain it...

 

Wirelessly posted

Same problem recently have u tried cleaning or replacing the IAC. Chenged mine and it went away.

 

sweet thanks for the advice i didnt even kno what that was until i researched it always saw it under the hood and had no idea what it was but anyways i cleaned it and seemed to have solved the problem havent heard the noise since thanks