sorry to bump an old thread, but could this be a common problem on say an 83 toyota with the 4 banger?
my truck runs like it has an unconstant spark, even after the voltage regulator, alternator, charging system wiring have been replaced and battery stays charged 
sounds like you might have a distributor problem. take the cap off and clean the inside of the distrubutor up real good. let me know if you need one. i've got a few laying around.
