Hello everyone, I have a 2004 F150 with a 5.4 and when i bought it, it had a K/N filter system on it. I am getting a high pitched whistling noise from under the hood now that it is getting colder here in Ohio. It doesnt do it at an idle, only when i am driving. If i let off the gas it goes away, until i get in the gas again. A tech at the Ford dealership i work at says he thinks it is coming from the cold air intake. I have emailed K/N and havent gotten a response. Has anyone run into this problem ? Thanx for the help.

 

I believe it has been narrowed down to the alternator. I get it too - approx 45-55 mph. Not lower, not higher than that.

I have a drop in K&N and I replaced it with paper for the winter months - no difference. Try a search for "cold squeal" or "cold whistle" and see what pops up.

Buddy had the same issue and replaced his alternator - hasn't experienced it since.

 

Pretty sure your correct on this one. Mine does it when cold and I first start the truck, does not do it while driving.

 

Yea mine does the same thing at around 2000 rpms. I read something before on here saying it was the throttle body spacer or something.

https://www.f150online.com/forums/ex...n-whistle.html

Hope that helps.

 

Not doubting you, but FordPartsGuy mentioned that its happening now that it's getting colder.

FPG, how long have you had this truck and have you experienced this prior to the temp change?

 

To the op....
The 04-05 5.4 3v are known to run lean from the factory.....I know you didn't put the CAI on but its making the truck run leaner.....you should also look into a programmer with custom tune to take into account for it.

 

I bought this truck new in 2004, then in 05 traded it in on a (dare i say it) minivan because of an expanding family. In March of this year i was looking to buy a used F150 and found the EXACT same one(ran VIN at the Ford dealership i work at and it was mine) so i bought it. So to answer your question, this would be the 1st time i have driven it in the colder weather since it was new in 04. Found alot of helpful post under, "high pitched whistle coming from engine in cold weather" on this website. Sounds like to me that maybe it is the alternator so ill throw that idea out to my tech. Thanx for the help

 

Yeah, let us know... and feel free to toss one my way as well!