My questions have to do with what I believe to be called the base timing, or when the wire under the hood is shorted to ground taking the control away from the ecu.
What would make the timing mark jump around when viewing it with a timing light.
What controls the spark timing in this instance?

 

It probably means the timing belt is loose. Take the top of the timing belt cover off and do an inspection. You'll probably find it is so loose you wonder how it stays on.

 

Hey jsinton, thanks for the reply. I just wish it was that easy. Unfortunetly that isnt the problem.

To better understand the situation, heres a brief summary-
About eight years ago the timing belt broke. And everyone should know what the outcome is. Well, it was all work and no play back then so it was pushed aside until two months ago.
With a 'rebuild' cylinder she started right up and sounded just like it always did- if just for a few seconds. Then the engine started surging and running rough. It was quite obvious that the exhaust manifold was getting to hot to quickly.
Troubleshoot, troubleshoot and more troubleshooting led me to remove the head and take it back to where I got it from based on these observations:
No cranking vacuum, low(10in.)and unsteady(wavered between 12 and 8in.) vacuum at idle. Oil coming out of the ports when the intake manifold was disconnected. Compression build up was not normal in that the first couple of hits were satifactory, but the rest were in smaller increments. It took maybe nine to twelve revolutions to build up pressure. All in all compression was fair. Had #2 reading about 171 psi. All the rest were about 180.
So the question based on what ya read here is, was I correct in assuming that the cylinder head is bad?

 

Breaking the timing belt is almost always bad. Assume the valves are bent.

Just shoot the thing and put it out of its misery.

 

When I owned a bunch of S-coupes '91-92, I was frequently asked to sell a distributor or the contactless timing parts of it. I was told the timing is based on a HAL-switch, which is a mechanical switch in a vacuumed glass tube... switch reacts to a rotating magnet. Having no experience of this particular problem I can't tell if the problem starts with occasional timing misfires first or the systems dies at once. This (Mitsubishi?) system was hard to replace cheap as the only alternative was to buy original parts.

CDI-ignition is triggered with the above mentioned HAL-switch or most commonly, with an inductive pick-up coil. The high-rev engines use light diodes to detect timing/firing. To avoid your problems, the triggering magnet or mirror is often placed on flywheel and the advance is electronically controlled in a black box or ingnition unit.

The timing advance is mechanical in your car as far as I remember. The distributor rotor shaft and the advance mechanism should not have any play. The parts should fit good into their supporting pins or shafts. Are the eccentric weights well supported, springs at their places, the advance mechanism is snug but rotates on the shaft when You turn it by hand against the springs?

Humidity, dirt or water in the distributor makes tricks like early firing also.

 

Hey jsionton- I will never 'shoot' this thing. No matter what it takes its going back on the road.
Its just going to be a little tougher then first anticipated.

 

Ok, well good luck with that. Your saying the timing belt broke EIGHT years ago and it's been sitting around ever since??? The list of things that could go wrong is by sitting that long is infinite. I'd prefer not to beat my head against the wall. But then I'm not in your shoes. I sincerely hope it's an easy fix and doesn't cost you more than a new junk car.

 

Well heres an update, just in case anyone is interested.
I live in Florida, so did expect the list of things gone wrong would be infinite.
The fuel tank and pump needed to be changed. Other then having to replace the head again due to no engine vaccuum, thats been it. The car runs good now. Got it moving under its own power and am putting brakes and exhaust on it.