My senior citizen SE7 04 with ~`150k mi started throwing P0306 codes (misfire cyl 6) last week and she's running like crap. Have really good 8mm wires and the Champs from AB in there with maybe 10k on them. Replaces the #6 plug, reset code and it came back, reset, repeat. #6 plug was not wet, just kinda overall black but not oily electrode fine. From what I've read here if it was a coil pack fail there would be 2 misfire codes to account for bad coil pack but not sure. I can reset the code and it runs smoothly for a bit but the next morning, for example, it comes back. Oil is clean, nothing coming out tailpipe, heads done @ 90k oh yeah and the engine has been ticking profusely (once warm) since about 100k so maybe this is the end of the line for the Beast. Front cover/pump replaced new about 20k ago as well.

Should I perform the tight rope hand crush manuever and pull out the SAI tubes and try to reseat plug wires or replace #6? I was able to replace wires using the non-intake pull method and a funked out screwdriver to seat the wires on the coil packs.

 

I never liked Champion spark plugs in my Disco but that's just me being posh. lol
Did you try swapping plugs of from either cylinder 2,4,or 8?

 

Yes, I put in a different plug. Going in tomorrow to eliminate wire.