I did a pretty extensive wire check too btw and found the sensor wire to the alternator had a bare spot so i wrapped some wire around it and put everything back together and it still ran like crap. I'm not sure if its worth sticking the old ecm in it or checking that wire some more.

I'll definitely take another look at those coils though and see if there'* something I'm missing. Can a coil be bad if the resistance checks out or would it be a ICM problem or ground problem?

Ohm checks with coils can help but the problem is probably not that the coil is completely dead but weak. The best way to test a coil would be to connect an ignition wire to the coil, a good spark plug with the proper gap to the wire and then pulse the coil like the ignition module would and visually observe the spark at the plug *unless you have a high voltage probe; I don't know what the primary voltage is to the coils; perhaps someone else could say.

From what I understand on this year model is that a misfire is causing the Code 18 to set even though Code 18 is for something else. This year does not have a misfire indication for the computer but a misfire can trip the Code 18. If you have put in good wires and plugs then I would suspect the coils as the source of the code 18. I had even replaced the Ignition Control Module on my car.

If this was my car, I would go to Ebay and find the cheapest set of coils (check the shipping fees as some will be cheap but high shipping) and replace them. That is what I did because I didn't have the money and needed to have a car; kind of hard to walk 18 miles to work. It may not be the coils, could be something else but the mechanic in Ca told me he had a 93 Buick with Code 18 he traced it to a bad coil and it was the same for my car. So that is two different ones that had Code 18 on a 93 Buick due to a bad coil.

Yes, have it dark as it may not be a strong arch, you may just see some stray voltage. When I got the Code 19 a few weeks after fixing the Code 18; which was not due to what the official GM shop manual stated, I looked at the engine in the dark and noticed that the number one wire had stray voltage that would travel the length of the wire, you could see it. No arcing, just sort of crawling along the wire. In the daytime it was not possible to see it. The wires I had on the car were only two years old but I had brought a cheap pair due to no money woes. I got a mid-grade set of wires and replaced them and the Code 19 went away and the car ran fine.

I know it is hard to throw parts at a car to fix it. I did that as well. I suggest the cheap coils because if you don't have the money to throw parts at it then we have to go cheap to see. However, if you can afford it, get the good coils.

I finally got a chance to look at the car in the dark and observed some arcing at terminal 1 between the plug wire terminal and the center part of the coil (with wire connected to Coil). Would this indicate a bad wire or bad ignition coil? I did see a bit of black on the inside of the spark plug wire where it contacts. I rotated it and there was less noticeable arcing but still some there (went from orange to blue)

If you have a wire to replace that one with you could check if changing the wire makes a difference. You could also swap that coil with another, they are all the same, and see if the problem moves with the coil (all coils in place of course). They are easy to swap out, remove the boilts and they just unplug from the ignition module. If the arcing follows the coil; with the wires not moved, then you know the coil is bad, just replace that one coil if you wish without replacing the others.

I switched the arcing wire to another coil and it continued to arc. I unfortunately threw out the old wires so I'm picking a new set up now. Fingers crossed

OK, you may have found your problem. I would go with a good set, maybe not the most expensive but not the cheapest either.

IT WORKS!!!

Never in my life did I think a single bad wire could mess up how the car runs so much. I ended up swapping out the front 3 wires and I'll probably get the back ones later. I knew the Buick still had some life in it. I drove it 2400 miles from Michigan to California last summer with no problems so I knew it had to be something stupid like a plug wire.

I admittedly went with the cheapest set at o'reilly'* for $20 but they have a lifetime warranty and were made in the US so hopefully they'll do (Last ones were from Mexico). Thanks for your help because the first good car that popped up on craigslist I was getting it.

RECAP FOR GOOGLE SEARCH FOLK:
If you have a code 18 check the coils or arcing on spark plug. Don't waste your time on the Crankshaft Sensor of Camshaft Sensor (I believe they have separate codes on the 93 anyways)