When I first purchased my 2004 Aviator a couple years ago I thought it seemed a bit lethargic for having the DOHC engine, especially at the higher revs. I did the typical maintenance items right away, spark plugs and air filter. I installed Iridium plugs and this seemed to help a bit. Next I cleaned the MAF sensor since I was struggling to get better than 13 mpg in town. I accelerate quickly, so I shouldn't expect great numbers, but this was about 2mpg worse than the 2004 Mountaineer V8 I traded in. So I did a cylinder de-carb using SeaFoam. After 3 applications the exhaust finally stopped filling my garage with smoke so that was definitely needed. And the responsiveness definitely improved, but still didn't seem happy above about 3500 rpms. All that effort was completed about a year ago.
Recently the fuel economy started dropping even more. I'm getting around 11-12 mpg in town. I decided to change the fuel filter and all four oxygen sensors this weekend. This seemed to help a lot, particularly at the higher engine speeds. The fuel filter I took out did seem restricted. Any everything was still stamped with either the Ford logo (sensors) or Motorcraft label (filter) so I suspect they all have 85,000 miles on them. When draining the fuel filter, it drained for a long time but never came out in a stream greater than half the ID of the filter. And if I reversed the drain direction (flow arrow pointing up) the fuel came out with an obvious orange tint.
I haven't put enough miles on it yet to determine if the fuel economy will be any better, but the responsiveness is much better. It's probably running like new now.
-Rod
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06-09-2013, 12:14 PM
