I have done a lot of searching on the site and found out that bucking is a rather common problem. I recently replaced my cam synchro because of the squeak and bucking. The squeak is now gone but the bucking is still there. The bucking happens intermittently at constant speeds, not while accelerating or downshifting, and not while on the highway, mostly 10-35 mph. I have found many different theorys on the site, i replaced my plugs and am getting new wires tonight, but in the meantime has anyone actually fixed this problem? How did you do it?
Its a 99 4.0 OHV with about 96k if this helps.

 

mine does the same thing with 140k on it while going around 35 to 40 mph, i think its related to the iac , i had a major bucking problem but plugs and wires from ford fixed that.
im curious to find out why!?

 

A little update, still hoping for some help. New plugs and wires did not help, still bucking, its very RPM dependent though. Between 1-2k rpm is when it bucks, and always while maintaining constant speed, not while accelerating. The bucks range from feeling like a bump to a full on jolt. They are intermittent, with the rpms being the only consistent thing, some days it won't buck and others it will every couple minutes. When it bucks the rpms also drop to close to 0 and then shoot back up, the harder bucks feel like bump starting the engine.