Question about 1998 Mercury Mountaineer

1 Answer

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*


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!



1 Answer

  • Level 2:

    An expert who has achieved level 2 by getting 100 points


    An expert that gotĀ 5 achievements.


    An expert whose answer gotĀ voted for 20 times.


    An expert who has answered 20 questions.

  • Expert
  • 45 Answers

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


1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

a 6ya Mechanic can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repair professionals here in the US.
click here to Talk to a Mechanic (only for users in the US for now) and get all the help you need.

Posted on Jan 02, 2017


Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

1 Answer

How do i drain my 98 mercury mountaineer gas tank? I accidentally put diesel fuel in n now it wont start!

You're gonna have to drop the fuel tank to dump it. Also, you're gonna want to change the fuel filter and flush out your fuel lines when done. You may still have to replace some of the upstream parts (fuel pressure regulator, 1 or more injectors, various seals).

Jan 26, 2017 | Mercury Cars & Trucks

2 Answers

I just purchased a 03 Mercury Mountaineer, it only has 32000 miles on it yet it the computer keeps saying the gas cap needs to be looked at. i took it in and the service guy has said it may need a new...

vacuum hoses can also degrade with time and not just mileage. id have it smoked to find the leak. itll be a lot cheaper in the long run for you to do so.

Dec 05, 2017 | 2006 Mercury Mountaineer

1 Answer

I have a 1998 Mercury Mountaineer when i'm driving down the road with the gas pushed in or the cruise control on it drives perfect shifts kinda hard tho but when i let off the gas or turn the cruise...

It could be your shift solenoid, or the wiring assembly for the shift solenoid, Ford has a TSB for it, it could also be a valve body gasket, I know the older explorers/mountaineers had issues with those as well.

Oct 21, 2013 | 1998 Mercury Mountaineer

1 Answer

Clicking noise when car is running 2004 mercury mountaineer

If your engine has the letters DOHC on the manifold, contact your dealer with your VIN#. If the sound disappears when the rpm approaches 2000 its the CAM PHASERS. The engines need the factory oil and filter and the cam parts can mess up without them. There is a recall with year and mileage limits.

Jan 01, 2010 | 1998 Mercury Mountaineer

2 Answers

Poor gas mileage on my jeep liberty

change your spark plugs if they haven't been changed in awhile. check your tires for the propper psi there should be a sticker on the inside of your drivers door that will tell you recomended air pressures go by this not the recomendations on the tires. also where are you getting you gas does it contain ethanol sometimes this can burn faster.

Feb 05, 2009 | 2005 Jeep Wrangler

1 Answer

Low gas mileage

change fuel filter and drive belt and spark plug wires if it does not have coil packs

Jan 21, 2009 | 1995 Mercury Sable

1 Answer

Can anyone help with an intermittent starting issue with a '98 mercury mountaineer?

If the motor turns over, but not start. Have the "crank shaft sensor" checked/replaced Ford part# 184768 $27.98 parts $230.00 labor). I chased this problem for several years. The crank sensor finally failed completely and the mechanic was able to find the problem.
Good luck

Jan 12, 2009 | 1998 Mercury Mountaineer

1 Answer

Poor gas mileage on my jeep liberty

Did this happen overnight or was it a gradual loss? Did you do any kind of repair before you lost the gas mialage? Is there a check engine light on or did it come on and go off? Did anything weird happen before the jeep got bad gas mileage? It's hard to diagnose a problem like this without actually touching the car.
Any other info might help me steer you in the right direction.

Nov 24, 2008 | 2005 Jeep Liberty

2 Answers

Jeep liberty gas mileage

to increase gas mileage make sure you keep on top of tire air pressure you can also have your tires filled with nitrogen instead of air also a K&N air filter does wonders and is good for lifetime worth every penny. another smart move is to use a fuel system cleaner regularly Lucas makes great products for this try local parts store.

Nov 24, 2008 | 2005 Jeep Liberty

1 Answer

Code p0401-exhaust gas recirculation flow insufficient detcted

these vehicles as well as every other Ford vehicle has had problems with the DPFE sensors going bad. Ford had a program for this problem but was limited to time and mileage. You can contact a dealer to see if it still qualifies if not the sensor will need replacement. this is very easy to replace

Nov 23, 2008 | 1999 Mercury Mountaineer

Not finding what you are looking for?
1998 Mercury Mountaineer Logo

812 people viewed this question

Ask a Question

Usually answered in minutes!

Top Mercury Experts


Level 3 Expert

77499 Answers


Level 3 Expert

5626 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22306 Answers

Are you a Mercury Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides