Invisable Speed Bumbs and Potholes.

[koldstart]

Ok, Under acceleration my explorer seems to pop and bump like I was to run over a speedbump or a pothole at a extreame speed. If I drive the truck lightly, I won't feel anything, and I'm able to shift gears very smootly, but when It comes to merging on the highway, climbing a hill, or anything that puts more than flatroad stress on my truck, I get these jolts, lurches. It's hard to describe. I have changed plugs, wires, fuel filter.. I can't figure it out.
It dos'nt feel like a severe problem, but it is very annoying to let out the clutch, step on the accelerator, and feel these bump like .. bumps - everytime I want to gain some speed.

Anybody brilliant here?

 

[410Fortune]

what engine is in your 99?
since you said clutch its either the 4.0L OHV or 4.0L SOHC

how many miles?

I would check your engine and transmission mounts, as well as exhaust hangers, u joints and the slip yoke in the front driveshaft

Check the rear pinion for play as well

 

[koldstart]

Yup! its a OHV 4.0, Manual Transmission, 4 Door. All the mounts look good, exsaust is solid, I can't find any play anywhere.
I wish i could describe it better, I hope it make sense to everyone. It's just a rough ride sometimes. Only under a load. I just cant figure it!. uhg.

 

[CDW6212R]

Maybe a ball joint, they are tough to check.

 

[410Fortune]

torsion bars and rear springs may be worn out
Shocks may be toast

ball joints, tie rods, etc may need attention

Its hard to say from your description

 

[koldstart]

Wouldn't those items be more frequently heard? This is only under a load, between 2000-4000 rpms, it almost feels like 4x4 is engaging temporarly, thats the feeling.

 

[adam4584]

mine does the same thing. it's only under load and it kinda feels like the fuel pump is cutting on and off real quick.

 

[410Fortune]

its quite possible your fuel pump is cutting in and out, check the connections at the fuel pump relay

 

[adam4584]

if it were the fuel pump wouldn't it do it in all gears? cus mine only does it in 2-5. 5spd man.

 

[koldstart]

well there ya go, we have the same problem exactly, I have a 5spd as well, under load. How do I check the fuel system? worth a shot for me, I hate this.

 

[fleettech225]

when was the last tune-up? it sounds like an ignition miss to me. does it do it when your cruising at normal highway speeds? check timing,(you'll need a scan tool for this) and ignition control module. could be as simple as this.
good luck!!

 

[adam4584]

nope not at highway speeds and not a timing issue no misfires plug wires ohm out to w/in factory specs. all but the ohm check courtesy or a snap-on modus scan tool w/ the latest software

 

[koldstart]

Yea, It drive fine at highway speeds, and the tuneup was prob done around 5000 miles ago. Plugs, Wires, .. Ya.. Help

 

[skoal_mint]

do you have the auto 4x4? if so did you already do the brown wire mod?

 

[koldstart]

Yeah, I have auto 4x4, and no I havn't done a brown wire mod

 

[koldstart]

Ok, actually, I just went outside, rulled under the explorer and disconnected the wiring harness to the transfer case. Took the puppy around the block, bang. It's gone, it accelerates smooth and evenly, just like I would want it to. Therefore there is a problem with the drivetrain? not the engine. What to do, what to check from here on forwarrd?

 

[koldstart]

help?

 

[Hoppy]

Probably safe to say that the transfer case it not working right.