Terminals A & B on a pre '96.
What else have you (or your mechanics) done, checked, or replaced? Have you looked at all your plugs to see how each cylinder is running? Are you going through any coolant. Checked fuel pressure? Checked injectors for a bad or clogged one? New plugs, wires, fuel filter, Clogged air filter?
Check for coolant in the oil- Luminas had a common issue to look out for, primarily affecting the 3.1 litre powerplant. This engine is prone to intake manifold gasket failures that can allow coolant to leak into the crankcase, where it contaminates the engine's oil, creating the potential for serious problems if the leak is not caught and corrected promptly. Coolant can also get into cylinders during running and stall the combustion. This problem can seem to appear with little to no notice.
The fact that its running does eliminate some variables, but give a few more details as listed above. If your car is running, but not running well, you should start by verifying the condition of the items you would normally replace during a tune-up, then proceed to more difficult items.