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10 MPG highway...what should I check?

4K views 8 replies 7 participants last post by  AlwaysFord 
#1 ·
Hello All,

I have a 2005 Navigator with the 6 speed transmission. I bought it used and, when I first bought it, I took it to Newport, RI from CT and then New Jersey from CT, both times getting very respectable highway mileage. Around 16MPG. However, since then, the MPG has gotten unbearable. I get 10MPG now.

My driving habits haven't changed. What can be checked or repaired?? Someone has mentioned exhaust leak and to check the plugs, which were supposedly replaced by the dealer when I bought it. I've used a Fuel Injection cleaner already too.

Any ideas??
 
#9 ·
Anybody have any ideas on how to tweak/improve the fuel mileage? I am at 13 average on my 2001 Ford Expy, it was getting 10, then I found a vac. hose bad going from the back of the throttle body up to the firewall somewhere. Now after replacing that its getting 13 and fixed my bank1 bank2 sys too lean problem, but would like to see it up to about 15 or 16. For instance... My grandfather had the same expy several years ago, and installed something like a computer fan in the intake, wired it all up, to come on when the cooling fans come on i think... and it brought him up to 19 city 24 hwy. he was at 13 city 17 hwy. but I am not exactly wanting to do all of that.
 
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