1993 4.0 litre bucks alot

[champwiz]

well let see if i can describe this one. it seems to bog a lot in all ranges then as you get up to speed. while stepping on it, it doesn't jerk as much until you get to cruse speed then in shifts into high gear and it really starts to buck. any idea would help. sick of driving this thing!!!

 

[Earl43P]

Welcome to The Ranger Station!

Bucking can be a lot of things, but I would go after the easy stuff first, especially if the truck is new to you.

Plugs (clean and gap / replace)
Plug wires (test / replace)
Air induction (tighten clamps, new air filter, clean the MAF)
Test for vacuum leaks (4.0 has issues with intake manifold gaskets)
O2 sensor (replace)
other sensors (test http://oldfuelinjection.com/?p=10 http://oldfuelinjection.com/?p=29)
replace fuel filter / test fuel pressure

Do the free and easy stuff first!

 

[champwiz]

same idea

I have the same idea I have done most of the items you have discribed but not all of them. will do more checking

Thanks

The Wizard

 

[redneckdanger]

bucking

I had a similar problem with my 90' 4.0. Do you have Bosch platinum plugs in it? If so throw them away and don't use them anymore. After going through the possibilities above, I changed the plugs (that were not but a few months old) and it cured the problem. Looking closer at them, I found that one of my plugs had a center electrode that was recessed back about a millimeter.

 

[RonD]

Yes, try Motorcraft or Autolite spark plugs.

The 4.0l likes these, it's not a matter of good or bad, it's works and doesn't work.

I have a 1994 w/4.0l and finally replaced the original plug wires this year, really helped the hesitations I was having, only 18 years old, some things just don't last


The problem you described probably would be this, but......losing power at higher RPMs can be a sign that the exhaust system is getting blocked up, back pressure builds up and engine loses power, this shouldn't produce "bucking", just a sluggishness at higher RPM.