Troubleshooting

[CC69Rat]

Originally Posted by MacGyver72

Plugs look good. Cap, rotor, and wires would be the next items to check. Check the routing of your wires. Often they are too close to the exhaust to last very long. You might also replace your fuel filter. Your issue could be one of fuel delivery.

I agree - sounds like it's hitting on 7 cyls. Is the plug in the picture your old plug? Did the problem begin after you changed the plugs or did you change the plugs to try to correct / troubleshoot (?) Did you put the same type plug back in it? you may have a colder heat range plug causing the miss.

Does it have headers on it? Check your plug wire boots. You might have one too close and when the plug fires, it arcs over to the header pipe instead of going to the spark plug, causing that cyl to drop out. = firing on 7. I had a 406 in an old Firebird a long time ago and it was bad to burn through plug boots. .. just some things to try. An easy way to check is to raise the hood at night. At times you can see the arcing as it happens.

Looks like a rich condition, that cyl is not firing and burning the gas causing the black smokey stuff to blow out.

.. just my .02.
Chad