To test this as well, you can use an UNLIT propane torch. If you notice engine RPM variances, then you know you've got air going in at the wrong place.

 

Hi there! Can you send us a private message with your VIN and Ford dealership info? I’ll look into this on my end. Thanks!

 

***EDIT: That's the #8 spark plug. Out of everywhere I've prodded, the sound is loudest under that lip where the #8 plug and the boot go.

I hope its not the spark plug. Last time I tried replacing spark plugs in a 5.4, I broke off numbers 1, 3, 5, and 7 in the head. Wasn't a good experience.

Also, the new PCV sounds much better through the stethoscope.
***END EDIT

Replaced PCV. Didn't fix the issue, but i did find the whistle. I don't know what this thing is called, just that it's going to be a ***** to reach.

​​​​​​FIrst photo for reference where you're looking in at.
Second photo, that yellow thing is what is whistling


.

 

I'm going to have to go look at my truck to see what that is.

 

It's the #8 spark plug. I updated my reply above.

 

...but don't leave yet. I haven't figured out what's wrong. Under that lip there is just where i could hear it the loudest with the stethoscope. The plug might not be the issue.

The vids I've watched tonight, if it was a blown spark plug, it'd be making a much different noise. And according to a recall notice I saw, a blown plug misfires and trips the check engine light. Neither have happened. Yet anyway.

 

5.4 2 valve plugs shouldn't break, that's a 3 valve problem. The 2 valve plugs loosen and blow themselves out if not torqued to 28 ft/lb. If you can get at it, pull the coil and make sure the plug isn't loose.

I think the evap canister purge valve is around there somewhere.

 

It is. You can see it in the pic, attached to the firewall. That's not what's making the noise, though i didn't trace the hoses back.

I also checked for a crack in the manifold. Didn't see or smell anything that points to that.

I'll tell signs and see if that plug or coil is loose, but the vids i watched, like "this is what it sounds like when you're truck blows a spark plug" and it didn't sound anything like what's going on with mine.

 

This is what ot sounds like inside while driving.

 

I was driving through a neighborhood and it just sounded loud and embarrassing, and since it didn't start the other night until iput it in gear, i thought maybe shifting into neutral would stop it.
It did not.
However, it also did NOT go away when i revved the engine up past 1500/2000/2500 RPMs. It has to be in gear for that to work.

 

When you accelerate under load, manifold vacuum is reduced. That may be why the noise stops. Might be a vacuum leak. I think there is a vacuum reservoir behind the battery and they tend to rust out sometimes.

 

I still recommend doing the UNLIT propane torch recommendation I gave using Roadie's suggestion in that area.

After listening to it, I believe it's a vacuum leak.

 

After another inconclusive session with the stethoscope, I found a way to fit my cell phone back in that area. I was looking for a vacuum leak. Then I pressed on the boot. Roll the clip.
I'm not sure what this means. Whether its loose or broken. I do know that I'm not equipped to take off the fuel rod and anything else that might be in the way.
I'll be surprised if it is just loose. I had an 06 with a 5.4 and the spark plugs in it had so much carbon buildup that you had to soak them in Break Free for 2 days, and even then you were still likely to break a couple off.

 

The 2001 engines are different from the 5.4 3 valve. You can tighten/remove them with no trouble. They are just hard to get to. I replaced the plugs in my 2002 5.4 2 valve taking my time. I did have to remove the fuel rail on the driver's side to get to a couple of plugs. Just torque them to 28 ft. lbs or thereabouts so they won't come loose and/or blow out again. The standard recommendation is to not use anti-seize on the threads but I did and they've been installed about 50k miles so far without blowing out. Knock on wood!

The fuel rail is easy to take off and reinstall. It just pulls loose after removing the retaining bolt(s). Just be careful reinstalling it to make sure the o-rings are in place so there won't be any air inleakage.

 

Should I be able to just tighten it and go on about business?? I don't have the money to replace them right now.

That's what i hear, but then i watched a pro with his own shop at home break two plugs off Now, conventional wisdom would say that if it backed out and is apparently loose, it should be able to go back in no issues. But i always have issues.
You say that, but I'm going to have to do this in a parts store parking lot because I'll inevitably need some other part and won't have a vehicle to use while this one is down.

I'll see about getting a proper plug socket.