Rough ridde; poor fuel economy: 2008 MKX w/123K miles

vazquecj

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Hi everyone,

I've got an MKX that I drive 60/40 Highway/City miles that is really starting to have me consider replacement. The ride has become unbearably loud-as if the window is open with the RPMs hovering at 2+ even when my foot is off the gas and I'm coasting at 20mph. I dont understand it - and no OBED scanner or dealer can identify an "issue."

The dash tells me I'm averaging 17.7 MPG, yet my fillups vs actual miles accrued is closer to 15mpg and I'm filling up every 2.5 days without having a lead foot or running the A/C constantly. I'm hoping the decreased MPG is tied to the sound my car is making, but no one seems to have a clue what's making it. The raised RPMs makes me think it's the transmission - anyone out there have any thoughts?

Appreciatively,
-Charlie
 
So I take it you have been to a mechanic? What did they say or suggest? Off the top of my head I'm thinking it could be the mass air flow sensor. Or possibly the idle air control since you mention high rpms. Or maybe both.
 
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