have a 1995 f150 when accelerating it starts to shake and vibrate between 40mph on up idili prefect..also notice when I strat it up from cold start it will cut off but after restart starts fi

Sounds like the vehicle may be experiencing spark plug miss under load. Check plugs, wires, and coil first as this may be the problem. Have the wires and Plugs been changed in recent memory?

thank u for response...I was thinking the same thing too. because the problem start happening when I changed the spark plugs ...now could this be that the spark plugs are not in right sequence...could this cause the effect of shaking and vibrating over 40pm

Spark plugs to not have any sequence to installation. Any individual one can go in any hole. However, there is a certain gap between the electrode and the tip which must be set before being installed. Also, the wires connected to the plugs have to be placed on the same plug they came off of. They have to be firmly attached. Usually one hears a little snap when pushed in. Also. a slight tug on the wire boot after installation should not remove the wire from the plug.