loud drone-hum

[Viper Command]

'97, 4.0 ohv, 5r55e, a/c-discharged, open airfilter element, 205,479 miles

durring warm up from idle to 2200 rpm there is a loud drone hum sound unshure where its comming from goes away before i can pull over and pop the hood, also its not rpm tone related, but when I jab the throttle for a few the noise does stop. on a side note my IAC is clean and it wissles at low rpms like a small lame turbo.


Any input is appreciated
Thanks...

 

[triumphrider-1]

Does it make the noise in gear and neutral?

 

[--weezl--]

my bet is u-joints

 

[Viper Command]

it does it in park, neutral, drive and reverse, and regardless of vehicle speed trans gear, so trans and U-joints, wheel bearing/brakes are out of question....


but there is no vibrations assocated with the sound.....

 

[aspevacek]

Let the truck set adn idle and see if the sound comes while it sets there witht he hood open. I had my camshaft syncronizer starting to go out a few years ago on my 4.0. The wife would hear th esound and befor ei could get to the truck it was usually gone. It was totally random when the sound would pop up or not. If that what it turns out to be for you I would suggest picking up the FORD part as I had some fitment issues with an aftermarket one, and it reset a code after it was installed and I had to pull the intake off to get it back out of the block. The one from FORD went right in and se tin the same position I had the aftermarket one the code went away.

 

[Viper Command]

Well now it wont stop making noise, its the cam syncro, ordering one from ford.....

 

[nando]

Well now it wont stop making noise, its the cam syncro, ordering one from ford.....

My Buddy had the same problem. i pulled the oil dip stick out by mistake while it was running and that humming sounds stopped. try and do that. if it works let me know ill ask my buddy what he did to fix it.

 

[Viper Command]

After $200 it turns out to be the effen PCV valve, $3 fix WTF

 

[triumphrider-1]

Well, atleast the cam synchro is good to go for while now...

How did you figure out it was the PCV valve?