Question about 1998 Mercury Mountaineer

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Gas mileage dropping

I've had this '98 Mercury Mountaineer for over a year. When I got it, it had 74,000 (actual documented) miles on it and it was pristine clean...definitely been taken care of. It was getting around 20 mpg on the highway and 16-17 around home (north Alabama, lotta mountains). In February we drove it 11 hours to Deltona, Florida and pulled back my fiance's new/old 1934 Ford pickup on a flatbed trailer. On that trip, we averaged 15-16 miles.

About a month ago, at 92,000 miles, I started noticing my gas mileage was dropping. I was getting 12-13 around home and it didn't do much better out on the highway. It started hesitating, and the 'check engine' light came on. I took it to my longtime mechanic (personal family friend for years) who checked it out and after putting it on "the machine" said a plug was fouling. We replaced plugs and wires, both coils (one had some issues that occured during the plug changing, I didn't understand exactly what happened) cleaned the injectors, checked all the filters, changed oil/filter, etc. It runs like a top now, BUT, I just ran the first tank of gas through it, and it got barely over 15 mpg on some fairly long trips without a trailer.

Any ideas what else to check? She runs great, no complaints (and I LOVE this vehicle!!!!!) but I gotta get better mileage than this, even though today I did buy gas for (drum roll please) $2.04. Who knew I'd live long enough that that sounds like a real bargain? *sigh*

Thanks!
Bobbye

Posted by on

  • bobbyesox Nov 15, 2008

    The fuel filter was changed, but I had suspected bad gas on the last fill up, I wonder if there is a "hidden" fuel filter. That happened to me once before on a mini van. The second tankful is about half gone and looks like we're still going to be about the same. It's running great though.



    Thanks for trying!

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While changing all the filters and things, did you change the fuel filter? It could have just been poor quality fuel which can be caused by getting fuel from the bottom of the barrel so to say. If the station you got the gas at was getting low there is a chance that there was water in the fuel. Normally this would cause the vehicle to run a little bit rough, but not always. I would run another tank of fuel through it and see what you get on a second tank.

Posted on Nov 13, 2008

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Posted on Jan 02, 2017

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