I'm making a (paritally) random guess here but it sounds like you have reached that point in this particular diagnosis.
You don't mention what year it is, but you should have either a hall-effect sensor or RPM sender that tells the computer when to tell the coil to fire. It reads the rotation of the engine at the distributor (hall) or flywheel I think (RPM). The plug into the wiring harness, or the wires themselves can short or fail intermittently, or the unit itself can fail.
There is a good step by step description in the 700 FAQ about how the ingnition system works. Yours may have different steps, depending on how old, but it may be helpful to read. If the specifics apply to your hear, there is a test there for the hall sender operation, probably in Bentley too.
On my 83 with chrysler ignition (white cap), I had problems with the hall sender. One (only?) benefit of the chrysler distr. is that the sender was pretty easy to replace, not like described in the faq.
Joe