Help, I have a 2004 Cadillac Deville base model that has a p0300 misfire code, it was running very rough, this happened 2 years ago too. Last time it was one bad coil and I replaced the whole bank and replaced the spark plugs, still had the problem, brought it to the repair shop and they found one of the new coils to be bad too and charged me $280 for just labor, this time I replaced the bank of coils that I didnt the last time and still have the problem. What terminals do you check for resistance on each seperate coil and what should the ohms be? I dont want to buy another rack of coils if I can use some of the old ones, the car has 187000 miles on it. I used a spark tester to test the coils, but that isnt a true test, under pressure is when they fail if they are weak. Im going to get a new set of spark plugs today to see if that helps, but I did that last time and it didnt.