So for about three days now my truck has starting a huming/whisteling noise. mainly when I let off the gas coming to a red light. I want to say its my altinator.. mainly because my friends went out in his car and he said it was his altinator because main sign is a whisteling noise.. any thoughts?? still drives the same, nothings different, no rpm drop, no low battery voltage..

 

check the leads to the battery. i know someone who had a loose negative cable. truck drove fine for a week making that whinging noise but we ended up stranded with a dead battery. thats when we found the loose lead.

 

what are we working on here?
are you you sure its coming from under the hood? does the noise go with the engine rpm during down shifting?

 

backing out of the drive way I can hear the noise I hit it into gear it stops momentarily(SP) then as I go to get on it a little I hear it. Then after a while I just turn my radio on and go on with my day. truck has 43 K on it I keep it regulary serviced, the computer check is showing all levels and systems ok. So I have no clue.

 

I had this exact same problem- humming or whistling sound coming from under the hood, I would goose the throttle and it went away. Mechanic at dealership said it was something called the IAC valve, told me to fix myself to save big $$. simple 2 bolt replacement part, was less than 50 bucks. replaced and no more noise. Hope this helps.

here's a thread on replacing: https://www.f150online.com/forums/en...iac-5-4-a.html

 

Hell with him Matt, - If the guy doesn't want to tell us what he's driving? - 73 posts and STILL hasn't filled his info in - Yea, - definitely isn't worth the time buddy.

 

didnt notice I didn't tell ya its an 05 F 150 King ranch 43 K miles on it had it for a month bought it from a dealer used. Excellent condition. It is under warranty for 6 months. But I can replace tha tthing my self if you guys believe thats what it is. But noticed last night
I didnt hear it any its coming and going.

 

your truck doesnt have an iac so thats not the problem. maybe an idler pulley or tension pulley. does the temperature seem to affect it?

 

Nope everything is just like normal i did a system check and its fine tomorrow after work Im going to take it to a altinator shop like two blocks away and let them run a test on it. But I don't think thats it either bc my battery is recharging fine. On the way to work today it didnt make the noise so Im clueless..