FerdinandF150

2011 5.0 STX - Stock

I cleaned the throttle body today with CRC TB cleaner and the MAF sensor with CRC MAF cleaner. I then reset the throttle body and let it relearn.

Took for a short 15 minute spin and was listening to it and could hear a whistle noise, it sounds like a dog whistle as it's high pitched.

It only happens when I accelerate and usually only for a second, but if I hold speed it will continue for a few more seconds. It doesn't do it while in park or neutral.

I can't say if this was here before I cleaned the throttle body, though I'm having some vague memory of it happening prior to today.

I took a short video.

It happens at 3 seconds and 11 seconds (excuse the last noise, there was a branch in the road.)

FerdinandF150

I've done a lot of digging, heard a few samples of noises, but nothing similar.

Something I've considered is that it could be the throttle body. Now that it's clean the inside plate is not sealed up as well without all the gunk in it, but I don't know enough about the throttle body to know how much it opens at which intervals.

I'll do some more digging.

FerdinandF150

The closest noise I've heard that resembles mine is an alternator whistle. Except mine doesn't do it at the start.

I should also mention temperature doesn't matter. Yesterday outside it was some 70 degrees and the truck had warmed for 20 minutes (resetting the throttle body.) Today it's 80 and it warmed for 3 minutes and still happened.

I'm leaning more and more towards the alternator. In the past I've had a couple instances of burning rubber smells.

FerdinandF150

Here is a video of the belts not under any load:

FerdinandF150

Here are the belts under load:

johnday in BFE

iTrader: (1)

Wish I could help more, but in your first video, I didn't hear anything. In your last one though, it seemed like your alternator was making some noise. Hard to be sure though with these crappy laptop speakers.

FerdinandF150

Thanks! Yeahhh. You have to have the volume up pretty loud. Crappy phone recording. d: It sounds like a dog whistle and didn't happen for more than 2 seconds.

I've got my dad listening to it as well. Prior he named off a few things I thought too; belt, alternator, vac leak.

SCORGE

Mine has a slight whistle under acceleration. Sounds like an infant turbo lol. I have no idea what it is, but it's done it for years.

FerdinandF150

Haha. Infant turbo. Thats a good way to explain it.

I tried running all my accessories, headlamps and have someone push the gas to see if anything dims, no luck.

How much play in the belt is okay? I can push it down some, but I didn't think it was outrageous.

Does your infant turbo sound relatively the same?

SCORGE

New belt, all idler pulleys are new, new AC comp. new tensioner. My sound usually peaks around 30-40 mph while accelerating. Probably been going on for 3 years now. I keep my TB cleaned as well. Same sound, faint whistle