right - first things first

Check the crank position sensor on the front of the engine - make sure this is clean and free from debris, is not damaged and that the wiring is spot on.

Then check the Phase Sensor inside the distributor and make sure that this is gapped correctly.


if you have replaced the ht leads plugs, cap, rotor arm and coil then thats good but to me, i'd put money on it been the crank sensor breaking down.