1996 Nissan Truck Engines starts to stall out after 20-30 m

To Technical people,

I have a Nissan Pickup King Cab XE 2.4ltr K? (107kmiles) series.

The Problem:
My truck runs great for about 20 minutes or so, usually on the highway.
then the engine starts to knock out. Weird but it happen when I hit a bump. When it is a
smooth ride it seems to work fine...
I pepper the gas and this kind of brings it back. but not all the time,but continues to die.
Again after the 20 - 30 time period. Short rides there are NO PROBLEMS at ALL..

If it dies it will start right back up again but still same issue.
Come to a stop enging wants to die....


I have replaced wires,plugs distribtor cap/rotor.
I have replaced fuel filter,nothing.
Replace all the belts too......

any ideas.

Brian
ratb7378@hotmail.com
847-849-7378

Truck Specs:
2.4 LTR
Air Conditioning
Power Steering ( I think Assist)
Idles and sounds fine...