Hi all,

Hoping someone here can help me with my Explorer. As in the title it's a 2002 SUV with auto 4x4, and I'm having a problem with the auto 4x4. I've done some 'net research and have had it in to get looked at but everything boils down to the 'net research isn't applicable or the shop couldn't give me a straight answer about it. I've read about the brown wire mod, pulling fuses, that kind of stuff but what I need is help with a diagnosis and then I'll go get the parts and just fix it.

The problem started a couple months ago when on the interstate making a 100 mile trip I noticed the 4x4 was trying to engage when I let off the accelerator at 65-70 mph, and stopped trying to engage when I stepped back on the gas. This was the first time this sort of thing had happened and when I got off the interstate I pulled it up to a midas, which was the only thing open at that time of evening. We put it up on the lift and I had the mechanics look everything over underneath to make sure nothing was going to fall out, I did afterall, have to try and make it back home that night. I didn't know for sure if I might have had a U joint coming loose or something, mebbe a belt blown on a tire, ect. Everything checked out ok mechanically so I drove it home.

On the way home it did do the same thing but not as bad as on the trip out. By pure luck I reasoned a few days later that on that trip I had put some air in one of my tires before I left. The tires then were worn and one had a small leak. I noticed that when the tire went down some, the problem went completely away until I put more air in the leaky tire, then it came back again. It took a couple of times of this happening for it to dawn on me that was what was making it try to engage the 4x4 during deceleration.

Sooo...I went to the shop and put four new tires on it, same size, height, ect. Figured this was going to fix the problem as I had talked to some folks and was informed about the speed sensors in the tires, and that tire size/pressure would affect the auto 4x4.

Now....after the tire change it wants to engage the auto 4x4 when I accelerate. The "bumping" isn't as bad as what it was doing before I changed the tires, but it's there none the less. It doesn't do it when at cruising speed, at least I can't feel it if it is. Where it does it fairly consistantly is from a dead stop and the tranny has shifted up into 2nd gear. There it feels the worst but goes away after it shifts into 3rd and OD. It's more noticable going uphill than going downhill. It doesn't do it if I'm cruising at any speed and mash the gas to pass a car or otherwise make it down shift at cruising speed.

One little test that I tried is pushing my 4x4 high button while it's doing it, and both before and after the tire change that would make it stop "bumping" or trying to engage. So no doubt it's the auto 4x4 and not some other problem.

I do have the ABS light on, which came on back in the middle of the winter, and hasn't gone off since. Folks are telling me that is because I have a bad wheel bearing which would do this sort of thing to the auto 4x4. But why the change from deceleration to acceleration with the tires changed? I also don't feel or hear a bad wheel bearing. All four wheel bearing were replaced a year ago right after I bought this thing, and I definately felt what they were when bad.

I've also heard I may have bad speed sensors, or a bad "auto 4x4 module"(over $300), and some other off the wall stuff too.

Any help sorting this out? Please?

Rah

 

Had the exact same symtoms as you state on an 03' 4X4 Explorer w/4.0l. It would bump on acceleration and was worse on hard acceleration. Turns out it was the 4wd control module.(The 3rd dealer we took it to finally found the problem) The guy at the Ford dealer said there was a TSB out on it and the TSB said to change the transfer case fluid as well. So to replace the module and the transfer case fluid it was over $400. The extended Ford warrenty didn't cover electronics. Another family member has an 02' Explorer with similar problems and $950 and 4 or 5 trips to the dealer later the 4wd control module was finally replaced. I would bet your 4wd control module needs replaced as Ford got a bad batch in early 02' and 03' production. It pisses me off Ford didn't stand good for a known problem but thats the way they are.

 

Thanks for the reply.

The one and only mechanic I really trust so far suggested that module which if I'm not mistaken is located behind the kick panel on the passenger side, (where the fuel shut off reset button is located).

He told me one from the junkyard is not worth putting in and that's convincing of him to say because he has the junkyard I would have bought it from. He told me to go to a dealer and get it, $300.

Before I spend that kind of money though, I'd like to know for sure that's what the problem is. Can this be run on the computer to find out if it's coding?

It would seem logical that if the module was bad it would be a continuous problem since it's electronics, once it goes bad it stays bad, no?. This problem has changed and is not entirely repeatable. It does vary in intensity and sometimes doesn't do it at all. Driving uphill makes it do it worse than driving down hill. I gotta wonder if there is something else causing it.

And I'm also looking at the possiblity that the bearing is bad up front and thinking that might cause the problem too...correct?

 

The '02s and early '03s definately had a batch of bad 4X4CMs. A shop with the proper diagnostic equipment (dealership) might be able to get a code, but as you note it's somewhat intermittent and those are hard to pin down. It is possible that a speed sensor or something else is causing your problem, but since it's an '02 I'm about 90% sure it's the CM. You could try draining the TC and adding new fluids to see if that cleans up the sensors.

I, and several others have purchased new 4X4CMs from directfordparts.com. That's the internet sales side of a Ford Dealer in Vegas. Mine was $160 which included shipping. I put it in myself in about 30 minutes (it's right behind the glovebox) and my Auto4X4 works fine now.

If you want directions to DIY let us know.

 

Explain to me, please, how these speed sensors work. I understand that I have sensors in the valve stems. Are you saying there are also speed sensors in the trasfer case?

My last truck was '76 chevy one ton, so I'm kinda behind the times............

 

If your machanically inclined I'd try to replace the module like rrgone said. Save some $$$ where you can. If I would have known then what I know now, I would have replaced the module myself. Live and learn.

 

Should add, that I'm not a huge fan of this auto 4X4, so far.........

 

Neither am I. I honestly don't know whats wrong with having 4X4 like the 01' and older explorers have. Less impact on the drivetrain too.

 

I come from the "gotta get out to lock it in" school, and despite bailing out into the muck too many times I've never felt much cheated by doing so. This Explorer is a nice ride, and not my first Ford, so I didn't mind the "deal" the bank give me as it was a repo in need of a home....

Too late now to whine about it as I'm knee deep in a payment book and not much room to move in a trade with something being broke. I do need to throw some extra money at it and fix the problem...

Any more suggestions would be much appreciated.......

 

I think Ford decided that the Explorers were not trucks but school buses and designed it for your wife, not for you.

 

Well that might be true but it's got the tow package and so far hasn't let me down pulling the camper, boat, welder, 4Wheeler...and does a fair job with the canoe on top.

It sleeps pretty well too with all the seats folded down and have used it on quicky huntin' trips a few times for that purpose.

It do suck though, at haulin' firewood.....lol.

 

Drain the T/C pull the 2 Hall sensors out and clean them.
Check for cracks in the sensor cases.
Reinstall sensors and fill T/C with fresh A/T fluid.
Cheap maintenance and usualy fixes the problem.

 

Aquanaut...

I'll do it, if only because it sounds like a good idea with such high milage.

Don't know if I should pat myself on the back 'cause I figured this out all by myself last night or if I should kick myself in the azz for not realizing it sooner...but it's "fixed".

The original problem was a worn tire issue, that was fixed with the new set of tires. I noticed that the new tires rode kinda rough, but really didn't think much of it since most of my "roads" around hear are just a little better than goat paths anyway. Well, I made a trip into town last evening and picked up a new tire gauge since my boy wrecked my good one. Bought one of those fancy digital ones and proceeded to check my air pressure.

There was 66 pounds of pressure in those tires......dayum.

Drain 'em all down to the 44 pounds listed on the sidewall and low and behold the problem went away. In all, the trip to town last night and this morning on the way to work covered about 50 miles and I couldn't get it to frig up not once.....

Them speed sensors sure are sensitive to tire pressure and size.........

 

Makes sense, at that pressure the tire contact area would be about the size of a tennis ball, any increse in torque would induce slippage, triggering the hale sensors to activate the elecromagnetic clutch in the T/C,.

Glad you got it worked out and for reporting back.

FWIW, I run my 6ply's at 40psi.

 

Also running tires at higher pressures slightly increases the circumference. It may have been enough to trigger the sensors.