Cadillac Repair: 1984 Cadillac Sedan Deville Spark Plugs, sparkplug wires, cadillac sedan deville

Question
I just changed the spark plugs, and spark plug wires in my 1984 Cadillac Sedan DeVille.  I changed them one at a time and made sure that I used the same length of wire on each one.  All of the plugs are gapped correctly (.060) And the wires are securely fastened to the plugs.  The problem is, when I drive it, the engine makes a loud popping sound and the car rumbles badly.  It didn't do this before I changed the plugs and wires.  I don't think that the wires in the wrong order, seeing as to how I removed the plugs and wires 1-by-1 and replaced them 1-by-1.  But it seems as if the timing is off with the plugs.  Any help?

Answer
Hi Josh,

      If all you changed are the plugs and wires 1 by 1 and didn't remove the distributor cap then what might have happened is you cracked a plug when installing it or it was cracked before and you didn't notice.

      If you have some insulated sparkplug wires run the engine and remove the wires 1 at a time and see which wire when removed doesn't cause the engine to run rougher. Then check the resistance of the wire with an ohmeter and swap plugs with another cylinder and see if that one runs good. If it does then the plug is bad and needs to be replaced. Otherwise disconnect a wire and ground it to the block. Then run the engine and see if it makes a differance in the way it runs.

     There is a possability that after the plugs and wires were replaced that caused a marginal cap to act up. I would remove the distributor cap and look for arcing/rainbows  inside the cap especially in the places where the coil screws are. What happens is the screws are alittle long and the spark will jump through the cap to the screws instead of the wire terminal because it is easier. The fix is to replace the cap and rotor and trim aprox. 1/16" from the screw and then install it. Also make sure the grounding strap is installed below the coil and goes into the cap center terminal.

       Hope that helps. Bill