Voltage decrease as engine runs is normal. As battery is recharged, the voltage regulator decreases voltage output of alternator to reduce charging current.

good luck

 

Sorry I have joined this conversation a bit late but did you get a code for the miss fire? Often times when the rotor pin where it meets the button is worn out for some reason it will jump spark, thus creating a miss fire if that makes any sense. If the cap or rotor have a crack replace. If the problem persists and you get the used plug wires only swap the number one cylinder to see if the problem is solved, if not use any of the other wires you get to swap the number on again, testing it each time. The number one is the shortest wire, thus all other wires will work, albeit too long. If that does not do it, listen to the injectors for even clicking as you may have a dirty injector.

Man I wish I could go to Australia right now just to get a break from things...

 

Thanks Texas

since then i am pulling plug wires and getting idle change on all cylinder, that made me belive that the problem is electrical, will have the hand on new distributor today.

Will do Turtle and let u know update

Most welcome, if u guys or any forum family come to Sydney please let me know, at least i wouldn't miss the treat for the great support you guys provide. World is a strange place and grass is always greener on the other side, opposite to Turtle, if i could go to New York for a break as my all family live there !