[Blue Bowtie]

Any check engine light? Has fuel mileage decreased?

I had a similar problem when one of my injectors was failing (134 CID just like your Cavvy). The injector did not spray fuel, but streamed it out the tip instead. The poor atomization at idle made it very rich, and it seemed like an almost completely dead cylinder. At RPM above idle it was just fine, and when the engine (head) warmed up, the extra temperature helped atomize the fuel better at idle and it was almost normal.

That may not be your problem, but the point is that it may not be something related to ignition. I'm guessing that most other people reading this would guess an ignition problem, and suggest that you check spark plugs for wear and gap, plug wires for conductivity and insulation damage, the two ignition coils for weak windings and flashover damage, and the primary connections. Of course, you should do all of that first, just to make sure the ignition system is in good condition. You should also check all hoses for vacuum leaks and the PCV valve for proper operation.

If all that reveals nothing, however, you might want to consider fuel delivery.