I have a 2000 Explorer with 201,000 miles, 4.0 ohv and auto tranny. I have noticed lately that my mpg's have been waning as well as an intermittant humming sound under the hood. When I got out to check the noise I noticed it was coming from the maf, and when I touched it while it was humming I could feel the vibration. The noise seems to happen more during cold days and since it's now winter in NJ, it is. The engine seems to idle rougher now and mpg's have suffered but runs ok when warmed up and on the highway. MAF problem or what?
On the same subject, the manual says the maf sensor and duvt body have to be replaced as a unit, but with all the cleaning going on in this forum, is that true or can I just replace the sensor if need be? TIA.

 

If it is making noise, replace it. Cleaning a MAF is for dirty ones, not noisy ones.

 

Most humming in that area are related to harmonics produced by the IAC, try cleaning it... quick test .. disconnect IAC, if hum stops, whalla!

 

Thanks guys, I will check on it over the weekend. If need be, I will replace.

 

I agree, with the Iac being the probable cause- may also be an induction leak from upper and lower manifold, the iac is very easy to clean, mine is a 2000 also and did not have the black pop of cap that some models have, so all i had to do was take it off and tease out the grime and dirt with some carb cleaner and loads of cotton buds.

The possible leaking induction manifold is also an easy fix, and involves just taking your time once you have the seals to remove the manifolds- take it easy they are plastic! and replace the o rings that seal them to each other and the head.........again not too much torque when putting it all back you could crack the plastic.
Rough idle in winter is a classic sign.
Good luck