Pontiac Repair: 96 Bonneville Ignition coil, ac delco spark plugs, fuel pressure regulator

Question
First of all thanks for reading this!
I got a 96 Pontiac Bonneville SE 3.8l which i bought half a year ago.
My question is, which ignition coil tends to fail first out of the 3 that are next to each other? My bonny started idling pretty bad on startup all of a sudden and its leading me to 1 of the coils. It feel like sometimes the motor is running on 3 to 4 pistons on start up and usually stalls or i just turn it off and recrank. Iv checked the fuel pressure regulator for any leaks and there was none (vacuum line as well).

Now iv done a major tune-ups myself on it such as: new AC Delco spark plugs (gapped) with spark plug cables, new upper and lower intake manifold (since it was leaking coolant), new air filter, new tension wheel, fuel injectors flushed, new PCV valve.

Im thinking of buying 1 new coil or used one from the scrap yard, but id like a professional answer.
I am also wondering why my fuel economy sucks real bad?

Thanks a million,
Sylwester

Answer
Hi There:

if the fuel economy is so bad it's because the cylinders that are firing are working harder than they should and the power you should be getting from the dead ones is not there so the fuel is wasted. You can check the spark on all 6 cylindewrs with a tool called a spark check it is basically a spark plug with a clamp on the side of it check all 6 cylinders (3 coils) for spark if you have a dead coil you can check the resistance of the coil across the towers where the plug wires go on should be between 4,000-6,000 Ohms and across the terminals where it sists on the ignition module less than 1 ohm. If those are correct measurements on the dead coil more than likely the issue is with the ignition module. Good luck :}