Intermittent Jerking on Isuzu Kb 260 D/C 1994

Hi all,
this is a great site, for manuals ...
can subeone help ... ?? WHEN DRIVING AT A CONSTANT SPEED, Cruising, No Load On The Engine, My Isuzu Jerks Intermittently, Like Fuel Starvation.whenever It Does This I Give It Full Acceleration to see if is a Fuel Shortage But It Accelerates Contantly With No Jerking At All.
I have fitted a New Fuel Pump and New Filters, New Ignition Coil and Spark Plugs and Plug Wirs, New Distributor Cap and Rotor.
This only Occurs When Your Road Speed ​​is Constant and You Are Not Accelering.
What Coud it Be ????
Kind Rens
Chris

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