What would cause a whistle sound from under the hood at about 1400rpms?It only does it at that range,not more or not less.I just started hearing it about a week ago.Is it the colder weather or whats up?Thanks,Joe

 

Could be a vacuum leak. Check the PCV hose for cracks especially behind the intake in the elbow. You don't have a TB spacer installed do you?

 

LxMan1,I went over all the hoses,I'm going to run out and double check behind the elbow.

 

Do you have an after market coldair intake?

 

check your throttlebodie and make sure its bolted tight, mine was doing that and I found a loose bolt so the gasket between the elbow and the trottlebodie was sucking air in and making a whistling noise, tightened the bolt and it went away.

 

The whistle went away the past couple days.I was thinking because of a little warmer weather,but I wonder if it is a loose bolt in the throttlebody,I will check.

 

Have you checked your radiator fan clutch? Mine is making sort of a humming noise and the sound changes with the spped of the fan. Several folks have told me it sounds like the fan clutch is going.

 

Did you ever figure out the problem? My 5.4 also developed a whistle recently, only when it's cold. Once it warms up it goes away. Also never happens on warmer days. It only happens in the 1900 to 2200 rpm range...sounds like one of those plastic tube kid toys that whistle when they spin around. It's been too cold for me to bother checking the PVC hose but I'm hoping that's the problem. My engine has 48k on it.

 

2000 model 5.4. Mine has had that same whistle since I bought it sveral months ago. 1900-2200 rpms under light load. I asked around where I live and others have the same issue ........ so I thought it was the nature of the beast.

 

REPLY TO ALL HAVE YEA CHECKED FOR A BROKEN exhaust MINIFOLD STUD.

 

BACK AGIAN. THE 5.4L whistle YOU HERE MAY BE FROM THE AIRINTAKE TO THROTTLE BODY. I JUST CLEANED THE *** OUT OF MY THROTTLE BODY AND ALL BREATHER LINES. I HAVE A K&N FILTER PACK INSTALLED. ANYWAYS I HEARD THE SOUND ON MINE AGAIN AND IT WILL BE HEARD AROUND 1400-2000RPM. BEING MANULE THE SOUND WILL COME BACK AT LOW RMP AND WHILE ITS UNDER LOAD IN HIGHER GEAR. IT WILL GO AWAY IN HIGH RPM.

WAY TO HEAR BY TEST. UNDER THE HOOD, TAKE THE BLACK COVER OFF THE THROTTLE BODY(THERE IS PINCH CLIP HOLDING IT ON PRESS AND PULL OUT COVER) START BACK UP AND PLAY WITH THROTTLE ON THROTTLE BODY MOVING BACK AND FORTH A LITTLE. LISTEN FOR SOUND AROUND TB AIRINTAKE.