Mine whistled one day about 2 weeks ago. It did in the morning and it was about 20 degress outside. And it did get louder the higher the RPM's got.

I currently have the k&n cold air intake and the edge tuner on my 2004 5.4 and it whistles so the other day I took them both off and put the stock intake on the truck and the truck still makes the noise. It is always when the weather is extremly cold though

I just had my Alternator changed and now my truck is so quite it doesn't seem right. My dealer said it was a refurb one but since I got the 7 year 75K miles I don't Premium care extend. I will just have it replaced again!

:rocker:

How about the IAC????
 

I was looking on explorerforum.com (for the wife's 99). There is an extensive thread on this, they found it to be the Idle Air Control valve. Some stopped the wistle by cleaning it, others had to replace it. I assume F-150's have an IAC as well. Just another thing to check for you guys!

I joined this forum because of this whistle. I have been threatning to strap the mechanic to the engine with the hood up and drive 60 mph down the road some cold morning. I am glad to see that I am not alone. I would like to throw out another twist. I agree that it is rpm related because I can hear it to a lesser degree in each gear and it is definitly louder the colder it gets. However the first time I heard it the temp was about 35-40. it was a foggy morning along a low river valley road. Each time I dipped down near the river into the fog bank the whistle started; and each time the road climbed up out of the fog the whistle stopped; immediatly. I am feeling that the whistle seems to be air intake related and is affected by the different air densities at different temps and humidity. However I am not anything close to a mechanic and have no idea how to fix this. Hope sombody discovers a deffinitive cause!

It can't be intake related because it did it with my OEM intake and now my AF1 intake.

The dealer thinks it's the windshield or a vaccum leak. We're starting with a new windshield first since I just got nailed by a rock on Sunday.

Duke

Are you sure you didn't accidentally install one of these...http://www.youtube.com/watch?v=Nnzw_i4YmKk

It appears the fix for the now "infamous" high pitched whistle is indeed replacing the alternator, just as others have done. I spoke with the shop foreman at the dealership where I get my FX4 serviced and he stated they have isolated the problem to the alternator. The fix is to replace the alternator with a refurbished one. I plan to have mine replaced in the next few days and will report back with the results. I hope this information helps.

My 03 Lightning made a high pitched whine when ever I got on the gas no matter what the temp was, so I sold it.

Mine did it yesterday morning. I think it has something to do with the power steering pump. That's where mine was coming from. Just a thought.


James

Well...I'm back and have good news to report. I had my alternator replaced and a new Gatorback surpentine belt installed late yesterday afternoon and I'm pleased to report no more high pitched whistle. It is gone!! As a test, I took my truck up to speed on the freeway this morning and it was completely quiet. It was -3 degrees here in Appleton, WI when I conducted my test. I hope this information helps others!

Excellent news Tru. If you're ever near MN, keep an eye out for a black F150 with dual exhaust and camaro style tips.

Duke

All, I just joined this forum because I'm having a similar noise problem, but now mine seems to be bit different. I have a 2004 F-150 SuperCrew with about 19,000 miles on it.

I've been hearing the noise at below freezing temperatures. Mine sounds most like what someone described as "someone using a saw in another room". It has a metallic sort of noise. It is definitely not the serpentine belts or anything.. I know what those sound like.

Up to now, I've just attributed it to cold weather. However, I've had a recent development that has changed my perspective. Two days ago, in sub-freezing weather, I began to "lose acceleration while accelerating". As I accelerate, it just suddenly stops accelerating. The RPM shoots up like it's out of gear and I'm basically coasting. This is under normal acceleration, nothing hard.
The noise is now gone, but at about the same point where the noise was during accelaration, it just seems to slip out of gear. I use the same maneuver that I did to make the noise go away (back off of the accelerator for a few seconds, then reapply) and you can feel it kick back in.

On the second day of this, I managed to limp to the dealer after having it "slip" on me 7 or 8 times. After two days, they are telling me that it's not doing anything nor is it making any noises. I'm frustrated. I believe it's something to do with the transmission or throttle, but I can't get them to believe me.

Any advice?

I joined because of the whistle as well. Here in chattanooga its been around 30 degrees lately and when i crank my 02fx4 in the morning, the whistle is there, but only at 1400 to 1600 rpm. It is consistantly at this range no matter what speed untill the truck warms up. Is the consensus still a faulty alternator?

I had the alternator replaced on Friday and the dealer said they've had to replace at least 15 lately. So far so good, no whistle what so ever.

I really think they should have a recall but are avoiding it to avoid the bad PR for a company that is already struggling.

Duke