1997 Ford Ranger 4.0 weird engine humming/whining

Hey, folks, please forgive the cross-posting but I found, in my search for this answer, some posts about Ford Rangers in both groups. I'll watch both threads for answers.
I've got a 1997 Ford Ranger with the 4.0 liter V-6 with a manual transmission and it's developed an odd whine from the engine compartment. It does it while both driving and just sitting at idle in neutral (makes hitting Sonic embarassing). I've used a stethoscope-type sound probe to try to isolate the sound and checked the serpentine belt idler, the A/C compressor (with the A/C off and on), the P/S pump, the water pump, and the alternator with no luck on finding the source of the noise. I then checked both valve covers and the main intake runner (coming from the air filter snorkel) and didn't locate the sound.
What I finally found was that there are two devices on the driver's side of the intake plenum (the black plastic-like thing that runs above the engine, coming from the rubber snorkel to the air filter); one that is cylindrical with an electric connection on it and one that is flat, about 2 inches tall by 3 inches long with an electrical connection to it with three wires.
That last device seems to be the source of the humming/buzzying/whining noise. It is about 1/2 inch thick (and 2" high by 3" wide, as I mentioned) and has two small hoses running to the bottom of it and coming from a tube that connects to the exhaust manifold. I don't know what it does, but I tried disconnecting the electric connector and that didn't make any difference in the sound. However, it seems to be the source of the noise, the best that I can tell.
Has anyone else had any problems like this? Can anyone tell me what that device is that I'm describing on the driver's-side of the intake plenum? More importantly, can anybody tell me what to do to get rid of the noise?
Thanks in advance.
--HC
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Seem to have found what it was...the Idle Air Control Valve, the cylindrical device I mentioned in my original post. For some reason the vibration didn't seem to be evident there but rather in the flat device below it. I took it to a friend who's a mechanic and he thought it was the IACV, so I took it off the truck (two bolts and an electrical connection) and cleaned it out with some Carb and Choke cleaner spray (holding it with the solenoid part above the valve body so it wouldn't flow into the solenoid part) and let it dry. Then I hosed it down with some silicone spray and worked the valve back and forth with my finger to make sure the silicone worked into the gap between the shaft from the solenoid and the body of the valve. Finally, I wiped down the inside of the throttle body (which says not to clean it because of some special coating it's got...but I did at the recommendation of my mechanic friend...but I used some diluted Simple Green to try to avoid damaging whatever magic coating Ford claims they've put in the throttle body) to try to minimize the amount of air that would need to pass through the IACV (I dunno if it makes any difference but my mechanic friend said to do so, so I tried it.
Anyway, after doing that the truck runs much quieter with none of the whine that I was complaining about in my original post. I checked with Autozone and they sell the IACV for this truck for only $41.99 and their site indicates that it's available in the store so if this cleaning and lubricating doesn't provide a long-term solution to my problem then I'll just replace it.
Hope that'll help somebody.
--HC
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They all need to be cleaned and lubed over time. Even if you bought a new one, you'd just be buying a clean one. Save your money until you need to buy one, and just keep yours serviced.
Spdloader

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I recall doinfg a search on the IAC sometime back and ran across a thread where the same symptom seemed to be common on some foreign car or truck... Was it GM or Jeep, cant recall? ;)
....

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Not sure, but the concept seems to be beautifully simple; we need a way to bypass the butterfly to adjust the idle of the engine and we want to be able to let the computer control it...boom...IACV. Sweet. So I would think a lot of more recent vehicles would have them...just guessing.
If I was to take an educated guess at what foreign stuff would have it it would be Mazda 'cause Ford and Mazda sleep in the same bad and have for years (Explorer=Navajo, B series = Ranger, etc.)
FWIW
--HC
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I'm thinkin' they ALL have them. How else you gonna do it with port injection.
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I'm not sure, I'm not an engineer by training. But, guessing I could see a throttle stop working (like on a traditional carbureted vehicle), and easily an electrically actuated gizmo (like a worm-gear setup) to move the throttle butterfly more open or closed as needed (like an automatic throttle stop). Who knows what else some engineer might come up with. I'm just saying that I don't *know* if all vehicles have them...not saying that it's practical, probable, or possible to do it any other way; just trying to be as accurate as possible so I don't mislead someone else who comes along and reads this; my purpose in posting my results was only to help others so if I don't bother to be precise and accurate in stating what I *know*, what I *think*, and what I certainly don't know then I'm not really helping anyone.
--HC
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