I have a 2000 F250 V10 4X4 4 door Lariat lifted with 35's and 72k miles on it. Have had it for 3 years, since 56k and as long as I've had it I've noticed an intermittent whining/sucking sound and loss of power, but not often enough to cause me any issues. Yes, I have replaced my plugs with new motorcraft ones and torqued them down shortly after buying it so I'm guessing it may be a vacuum issue or leak somewhere. The interesting thing is that It is much more noticeable, as is the power loss, when driving up to and at elevation. Anyone have a similar issue or experience? Since it only does it under power, I can't replicate the sound when parked. Another interesting thing is that when I give it more gas it goes away. Anyways any help will be appreciated. Thanks fellas

edit: When I first got it I did Take it to Earnhardt Fords service department and payed for a mechanic to look it over, no engine codes

 

When it's making the sucking sound under power, does the HVAC switch to blowing from the defrost vents? If it does, that's a pretty sure sign of a vacuum leak.

 

Check your intake filter and the connections where your intake meets the filter box, and the manifold. If everything looks good there, you're probably losing vacuum somewhere. See if the truck does the same thing in park revving it up as well. Would make it easier to find also.

 

It only does it under power/while driving... cannot recreate the noise while parked

 

I just drove it around and could not tell any difference in the HVAC system when it makes the noise

 

could it be throttle body related? I was thinking of pulling it, cleaning it, and replacing the gaskets

 

would it be an ordeal to go through and locate a leak in the vacuum system? or is that just replacing the hoses? thanks

 

Seems unusual that you can't replicate it simply by revving the engine while parked, also since your HVAC isn't jumping to defrost it's not really likely its a vacuum problem. Hard for me to guess as I'm just a DIYer. Inspect filter? Inspect/replace fuel filter?

Lot of people have issues with fuel pumps, might be worth getting the fuel pressure checked. I know I've read a few threads where they would have fine pressure while sitting/revving but lost pressure while driving/towing.

 

thanks johnfist yes it is odd, I will look into those fuel pump threads

 

https://youtu.be/EtXZbSA01ko

I wasn't able to post the video here so here's a link. I am wondering if it's coming from the headers as my mechanic friend said they look like they are leaking. The sound is coming from the driver side I think but the right side has 2 broken exhaust manifold bolts busted off. Could it be as easy as new headers? Maybe the metal gasket is acting like a reed and causing sound with the leak?

 

I would think if it were exhaust you'd be able to hear it without driving down the road. Also, a minor exhaust leak wouldn't cause a loss of power.