I have a 02 supercrew 5.4 , its made this noise since I got it for about 3 years now. Makes a ringing or bell like fluttering sound only under a load, does not do it at idle or reving in neutral, which makes it hard for me to determine where its coming from? Does not seem to affect performance I guess,.

 

Do you here anything at all right after shutdown - like air bleeding off ?

If not , I would have to say your hearing an IAC noise. BUT, it could be a vacuum leak as well. Will it make the noise if you accelerate from under the hood? Or does it have to be in gear?

 

I dont hear anything bleeding off, and it has to be in gear

 

Do you have a after market intake ?

 

no, it came with a air raid tb spacer but I took that off thinkin that was the source but it made no difference, Ive also checked for vaccum leaks by sprayin starting fluid around hoses, etc. and cant find anything.

 

It could be the PCV valve - I bet that's it. Keep in mind that the PCV valves for these trucks are not all alike. The Motorcraft PCV valve is the one you want vrs. those imitation shiny silver deals.

If not, try using propane to detect the leak. That's a better all around method.

 

Try checking for recalls on your trucks exhaust system. The problem you are explaining sounds much like a problem resulting in lack of clearance under load between the exhaust and frame/supports or a resonance in the pipe material. Cadillac had this problem in the early 90's, GM trucks had the problem also after 2000, and it could be the case here. Cadillac's issue was the exhaust hitting the frame under load conditions and was a "recall". The GM truck issue was the fact that the car and truck industry want that "DEEP" full flow exhaust sound because it helps them sell. The larger exhaust pipes and air flows (Especially in cold conditions) can produce a "RING" or "HUM" sound generated more from resonance in the pipe rather than a "mechanical issue". This "resonance" issue seems to be worse with higher grade stainless exhaust pipes versus steel. Hope this helps...

 

Check the flexplate. It could be hitting something under load. Are the torque converter bolts all tight? A loose one will back out and hit.

Regards

Jean Marc Chartier

 

What grade fuel do you use? It could be a pinging type noise caused by low grade fuel. Kinda hard to tell without hearing it.

 

I use regular fuel, but ive tried all types with and without additives

 

It may be a prob with the pulleys, possibly a bearing going bad???

 

I should be able to run that with the belt off for a sec right? thought I seen some talkin about that.

 

Have you tried a tank of high octane (91 or higher) PREMIUM fuel?

 

yes, tried that as well.:o

 

I agree with the pulley/bearing idea. Start with the easy ones like idler and tensioner. It is very easy to pull these and you dont need to run the engine with the belt off. just take off the pulley and spin it on your finger. You will be able to feel/hear if it is no good.