1998 5.4 4x4, low mpg, vibration, etc...

[kargh]

Hello All,

New to these forums. Just registered and I have a few questions for you fine folks.

I imagine some of the information I'm asking about is located on these forums in one post or another, and while I intend to dig through everything, I figure it might take me quite a while and hopefully someone will be able to give me a quicker reply.

So, thank you in advance for your patience.

Heres what I have:

1998 Expedition 4x4 5.4L (non-Eddie Bauer)
118k miles
New tires, brake pads, replaced worn tie rods and ball joints
No known issues at the present time

Currently I'm getting about 7.5 mpg highway. This, I'm expecting, is -way- lower than what it should be but from what I can tell (or hear) everything is running good. I imagine the vehicle is in need of a general tune-up and that might help with the low mpg. Aside from a general tune-up is there anything else you might suggest to check into?

Second, and this only happens occasionally, when I turn a corner it feels like the vehicle is being pushed forward as much as it is turning so theres this almost skidding-vibrating sensation... as if too much power is being pushed out while turning. I have a 3-wheeler that does the same thing if you don't have enough weight to the front of it. If anyone knows what I'm talking about, is there a fix for this? Its like turning quickly on a gravel road and you slide through the turn but this is happening on concrete and at slow rates of speed (eg: from a stop sign or lights).

Braking. A few times this winter I lost (or... possibly gained) my brakes. By that, I mean, that when I went to stop my brakes were hard as if someone were pumping them until fully pressurized. I suspect that its the anti-lock system going haywire. Instead of a nice gradual pumping action, it goes very fast. Anyone else have this happen? Is it the sensor going bad? Someone once mentioend to me that it gets dirty/rusty and needs to be cleaned off but I've not yet looked for it (and have no clue where to look at the moment either).

A few other random inquires: Is it possible to disable the automatic door locking mechanism that causes all but the drivers side door to lock when you exit the vehicle? If theres anything that frustrates me more on a daily basis, I don't know what it is.

Well, I guess there was only one at this time.

Again, thanks for your time and patience. Hopefully I can find a few answers on my own on these forums.

-- Jess

[TBIRD430]

How is the maintenance up on ur SUV? New plugs, fuel filter, air filter, plug wires, fuel induction system clean, tranny fluid flush, front & rear diff flush?? Also do u still have stock wheels/tires, correct air pressure in tires, and a stock ride height? All of these things can affect ur MPG. Finally, how do u "drive"? Slow take offs and gradual braking, even using ur SUV's cruise control system are ALL positives....

[kargh]

Originally Posted by TBIRD430

How is the maintenance up on ur SUV? New plugs, fuel filter, air filter, plug wires, fuel induction system clean, tranny fluid flush, front & rear diff flush?? Also do u still have stock wheels/tires, correct air pressure in tires, and a stock ride height? All of these things can affect ur MPG. Finally, how do u "drive"? Slow take offs and gradual braking, even using ur SUV's cruise control system are ALL positives....

Hey, thanks for your reply.

I had a pretty long and detailed post written but then my system locked up and I lost it so I'll try to redo it to the best of my memory.

I bought this vehicle used at a Ford dealership at 99k miles. Since then I've put on 18k. I doubt they did any sort of maintenance at the dealership besides going over their checklist and I know that I've only done oil, filter and air filter changes on a regular basis.

I would like to state, at this point, that I am no where near even being considered an amature mechanic. My expertise is in networking and programming but I'm not afraid to dig in and learn through doing.

This weekend, pending weather and family obligations I intend on doing a diff change. That looks pretty straight forward.

I would like to do a plug and wire change. That'll take a bit more time and hopefully I can get to it this weekend. I've done some research for what might be best to use but unfortunately I didn't find much. It seems that its all personal preference unlike computer components. Any suggestions would be appreciated.

A tranny flush would be in order also. I'm fairly certain I can handle that. For all I know, it might not have been done in 50k miles or more at this point. Never changed or looked at the fuel filter or the fuel induction system (infact, for that one, I have no idea what to do or where to look at the moment).

The tires are new. I just replaced them last fall. They are inflated to the correct psi. I didn't check the ride height. I didn't realize that was something I had to or should do. Is that something I can adjust myself if its off? I'll see what I can find about checking it.

I'm a huge believer in cruise. I use it as much as possible. Infact, people who don't use it drive me crazy with their speed-ups and slow-downs. I try to be easy on my starts and stops but it seems this truck just wants to go when you hit the gas. Actually, one thing I've noticed is theres a bit of a stuck point when first pushing on the gas pedal. It doesn't have a nice consistent pressure. If I'm taking off from a light or stop sign, a lot of times when I press the gas, I have to press hard enough to "unstick" it and that causes me to take off with more of a jerk... faster than I'd like. Thats probably something I should look into as well. Suggestions?

Anyways, thanks for your time and advice. I've been slowly trying to do as much general maintenance as I can afford on my own. Replaced the tires, tie-rod, ball joints, pads, rotors, etc last fall. Now focusing on other aspects.

[TBIRD430]

Replacing the fuel filter would be ALOT easier than the spark plugs and wires. I recommend u use ALL Motorcraft parts as well. Just set aside a whole day 1 weekend and take ur time, do 1 cylinder at a time so u keep everything in the right place. U will need a 5/8" deep socket, a swivel adapter, some dielectric grease (put on BOTH ends of plug wires), and several more varying extensions.

For that stuck peddle feeling a simple cleaning of ur throttle body would suffice. I would buy 2 cans of Seafoam brand fuel system cleaner (at most auto parts stores, white metal can w/red letters). Add one can to 1/2 a tank of gas and run the 2nd can through ur SUV's power brake booster vacuum line (going to the intake manifold). U will need to do this outside with the truck running, then go drive the heck out of ur SUV (for about 30 minutes). Trust me here, the SUV will smoke, stink, even rattle some, but this is ALL power robbing carbon being BLOW out of ur engine.

As far as my inquiry on the ride height, I just meant to question if this SUV had a Lift kit installed or sat at stock ride height.

[kargh]

Much appreciated Tbird.

Not to sound like a total noob but when you say add a can to the vacuum line, I'm guessing you mean to detach the intake manifold vacuum hose from the housing and stick the hose into the can and let it suck it up?

After it sucks it up, I assume I reconnect it and then drive it around until it stops pitching a fit?

Thanks for the rest of your advice. I'm going to try to knock out a few of the items on the list (fuel filter, diff change, tranny flush, plugs/wires, and this additive) this weekend.

[kargh]

Friction modifier.

This must be something that you have to go to a Ford garage to buy or order online. Seems that no place I look carries it (Checker, Autozone).

That generally the case?

[TBIRD430]

You are correct about the proceedure in adding the Seafoam treatment to ur engine. After the whole can has been sucked dry, kill the engine, and reinstall everything (usually 15 minutes), then drive the heck (safely of course) out of her soon.

The friction modifier is used only if u have a limited slip rear diff (with clutches). Most 4x4's have this design rear diff, and I only know of the Motrocraft brand available only at the Ford dealer's. One bottle will be enough to do the rear diff....

I was also thinking, now would be a great time to replace the PCV valve on the right valve cover, it's cheep too.

[kargh]

Just to be clear on this, I'd remove the vacuum line from the power brake booster or from the other end? I'm not sure which way vacuum sucks

I assume it sucks it into the intake manifold, not into the booster, but I've been wrong in the past.

10-4 on the PCV, going to replace that along with the serpentine belt (heck, might as well as long as I have half the engine torn apart to do plugs).

Thanks again for your help.

[TBIRD430]

U are correct again, remove the vacuum line from the booster, clean the hose with a rag and place inside the Seafoam can. Make sure u run run vehicle OUTSIDE, as there will be a foul smell and a smoke show (if carbon build up is really bad).

Have fun this weekend, and post back to us afterwards.

[kargh]

Ok. Thanks again. Will do.

Looks like its going to be a busy weekend