I have a p0300 code in my 2004 cadillac deville. I have changed the front bank of ignition coils with a new set and swapped the back set with what i thought were good coils and it still runs like crap Can you test these coils with a multimeter? If you can which terminals do you connect to and what ohms should they read? I already tested them with a spark tester and cant tell if one is weak or not, because under compression it is a different story. I also have had a problem where my car would shake terribly at 68 mph and above. I had the tires rebalanced and it didnt help, changed wheel bearings, didnt help, finally I looked at the top front strut mounts and they were egged out in the rubber part and very loose, changed them and no more shake!

 

Hi Chris. Welcome and get ready to spend a ton of money on your worthless car. I'm sure if you didn't purchase an aftermarket warranty you will be willing to dump it in about a year of agony!!!!!!!!!!!

 

I have had the car for over 5 years and put 146000 miles on it, replaced one side ignition coils once, now the other side and had to replace the fuel pump, otherwise no problems. I consider that to be pretty good, im sure others have had more problems, but I do like the cars, just the need for special tools for many things is irritating. I just need to figure out how to check the coils with an ohmmeter and I have yet to find that information, or buy a coil on plug tester, either way it would be cheaper than bringing it in to a repair shop, I found a coil on plug tester for $86 on amazon, its the type you set on top of the coil when it is running. Otherwise Champion Auto Parts store will test them for free, but I have to drive the car there to do it, and it is running like crap.