Was searching for diagnostic info on sensors when I ran across this TSB.

It caught my attention because my 2001 EB makes a soft "whining" or whistling [not exactly a whistling noise, it's softer, or like an owl and the sound changes pitch with RPM changes] sound at +/- 30 MPH.

The TSB says:

"Some vehicles equipped with the 5.4L 2V engine may exhibit a "whistling" noise from the formed nylon tube in the idle-air bypass flow circuit. This may be caused by air flow passing through the sharp bend radius of the original tube assembly."

I'm wondering if anyone else has heard this and what it sounded like at what speeds, RPM's, etc.

Here's the link:

https://www.ford-trucks.com/tsb/full...hp?tsb=02-10-8

 

It's the whistling from my supercharger that drowns out the noise from anything else.

 

The 98 models may be subject to this too. I get this noise at light throttle on my 98 Expy. I just replaced the belt and put in a new IAC and i know every is working properly so i just ignore the noise. Mine sounds like a low whistling noise though. I guess its just another thing to live with, just like that cold start up knock noise our motors suffer from .