Hey guys, thought you may be interested in this one.

One of my friends recently purchased a 2002 4.6l Explorer Limited (Auto, 4x4, 3.73)
He had a problem with shuddering on light to medium acceleration, usually under a bit of load.
It felt like the car was misfiring.
So we replaced all the things that usually induce a misfire, leads, plugs etc.
Problem was still there.

I was confused.
I thought it may had been the auto then.
By pure chance, when we were taking it to the auto shop to get looked at, while it was shuddering accelerating from the lights, I hit 4x4 High on the 4x4 mode selector.
Shudder went away!!!

After a little bit of investagative analysis it appeared that the threshold for activating 4x4 while the vehicle is in 4x4 Auto is a little to acute.
I removed the 4x4 module (behind the glovebox) and the problem went away, as the vehicle was now running 2wd while the selector was in 4x4 high.
I felt this wasn't an appropriate fix, so I got some of my electronics friends to create a module that I can flash with our computer equipment (the standard module isn't flashable) and I created a 7% differentiation in the activation (i.e. the front ABS sensor has to be going 7% slower than the rear one).
It solved the problem.
The 4x4 may take a little longer to activate in the ice, and snow (maybe 1/4, to 1/2 a wheel turn) but the problem is fixed.

Thought this maybe useful to some of you guys that are experiencing a similar problem.

BigF350

 

Bump

Anyone esle experiencing this problem?

 

I had a 4wd engagement problem on my 04 explorer. The dealership first replaced the abs/speed sensor, and that didn't work. Next they installed a new pcm, and I haven't had any more trouble with it.

 

My question would be this:

Did you check to see if the speed sensor in the rear differential was reading right??

This could have created the problem as well.

 

I have to agree with bigf350, the sensors on my 02 Explorer 4.6 seem to be a bit on the sensative side. I thought my abs/brakes were shot. Luckily I had a 4 wheel alignment done before the brake job. The brakes feel like new again. My guess is that the ABS/Speed sensor was being thrown off by an out of whack alignment. Now that's sensative !! Come to think about it, I was about to install 4 new plugs and change the pcv valve, and a tranny flush because of a shutter/misfire. I'll have to check to see if that's gone as well. If so, I'll have to push alignments to the top of my check lists !!

 

The speed sensor was reading correctly.

I would also check the tyres rolling diameter and tyre pressures to confirm they are similar, and within spec.

 

BIGF350,
I have a 98 Explorer that is doing similiar things. Mainly noticable when accelerating up a hill and the tranny is close to shifting from overdrive to 4th. (5R55E tranny) The strange thing is I can drive it like this for an hour, stop and get gas, start it up and it shifts fine. Problem gone until I stop again and let it sit overnight. I too can put it in 4 high and the problem goes away. Where did you find the module (under or behind glovebox) and will it cause trouble codes to remove it to test? I have two different types of tires on the front versus rear and wonder if there may be a size difference that becomes less of a problem once the tires heat up and expand a bit. Any ideas? I replace both transfer case sensors but no luck. ARe you saying the ABS sensors can read axle speed for the 4 wheel drive also?
Thanks,
Rob Rike
98 Explorer XLT 4.0 SOHC and auto select transfer case

 

The reason (well this is my theory anyway) is that the oil in your transfer case is more viscous when it is colder (i.e. vehicle has been sitting for a while).
As it requires activation of a clutch pack to engage 4x4, the clutch only tries to activate a small %, as it is only detecting a small amount of wheel spin.

When the oil in the transfer case is hot (less viscous) it will cause the clutch to slip, as it is not applying full load on the clutch, and the user (yourself) will not be able to notice it when it is trying to activate. When it is colder and the oil is more viscous the clutch will be able to grip even with the small load, and you notice the shudder.

You shouldn't create any trouble codes by removing the 4x4 module I don't think.
I am not sure where it is in the older Explorers though, but I have heard that they can suffer the same problem.

I would also check the diameters of the tyres when they are hot, and when they are cold.
That could be causing it as well, one tyre type being larger than the other, and when they heat up they expand to be the same kind of size.

 

BigF350 - You described my problem to a T. It feels like misfiring under hard acceleration, and I was about to change out the plugs, etc. I'm going to have to hit the button on the way home to see if it fixes it. So if I understand you right, for some reason or another it thinks the rears are slipping so it tries to put power into the fronts? I really wish these things had a dedicated 4x2 setting. Auto is nice for winter, but I'm sick of the computer deciding everything for my truck. Heck, that wonderful "traction control" in my Mustang wouldn't let me get up my driveway in light snow. But once I turned it off I could get it up just fine working the clutch.

By the way, I have the same setup as your buddy. 2002 XLT (not limited) with the 4.6 and the 3.73.

 

So if I understand you right, for some reason or another it thinks the rears are slipping so it tries to put power into the fronts?
Yup, thats correct, and the transfer of power to the front causes the shudder, or "misfire" feel.

However, the vehicle may still be misfiring, but whenever it decides to "shudder" - I found it would do it most with light/mid acceleration under a slight bit of load, just hit the 4x4 high button, if the shuddering stops, its the problem I am describing.

Unfortunately the Explorer is not mine, but a good friends (I just fixed the problem for him), I wouldn't mind one though...