I just noticed this since I fixed my passenger head, but here goes. When I let off the gas I get a whistling sound coming from the front of the truck. I can't reproduce it while the truck is sitting still. I don't think my wife noticed it, but I notice all kinds of noises. (I think you start to do that once you take on a major project...) It's just annoying. I don't think there is a power problem, but I could be wrong.

Any ideas where the whistle is coming from?

Doug

 

Cold Air intake Kits do it!

 

BLU be true ^^^^^

K&N Filter, Airbox Mod and Silencer Removed

Check your air intake mods. Do a search on "whisling sound". Bet you will find your problem there.

Good Luck,

Bill

 

On the K&N FIPK, the "air bi-pass valve" causes the whistling sound. Saw off the nipple and use the provided rubber hose w/ hose clamps. It worked for me!

 

I have a similar whistling sound. I have a 2002 F150 FX4 with 5.4L (completely stock) and I get more of a whistle at startup but also throughout the time until the engine has warmed up and sometimes longer. It's much worse (in volume and duration) when it's cold outside - last week as low at -5F. The noise will come and go with acceleration and at steady throttle, but can't really reproduce it standing still, except when it's really cold outside. I've not been able to pinpoint it to any one system - for instance, powersteering pump, although it's very loud outside the truck. Not having the time to track it down, I took it to the dealer and they have changed a PCV hose (hard plastic to rubber, as part of a Technical Service Bullentin) and a heater modulation valve and hose. They now think it's the IAC (not sure of the acronym, but part of the intake system), which sounds more likely as it usually goes away after the engine is warm, although I have heard it afterwards. However, before they try this or something else that may or may not fix the problem, I wonder if any of you have any ideas. This has become very frustrating especially since I first heard this whistle after only 3 months and 3300 miles - of course, about the time that it started to get cold. That was 1,000 miles and 3 months ago. Thanks.