Just changed 2 plugs for the first time on my 2001 E320 at 97K. Indie's SDS indicated an "almost misfire" on cylinder 5, so I decided to change both plugs and wires on that cylinder as a temp solution. I want to change all plugs and wires when I reseal breather and valve covers soon.

Anyway, the 2 original plugs were fairly tight coming out but nothing too scary. The new ones were also pretty difficult to thread in by hand given the dark recessed hole and slippery ceramic. I spent about 3-4 minutes per plug spinning each what felt like 1/16 of a turn at a time by hand. I then used an extension and spark plug socket to tighten them up further. This is when I noticed several more turns of the rearward plug compared to the forward plug. I initially thought I made more progress by hand on the forward plug which would explain the fewer turns of the socket. I then attached the torque wrench at (18-20 ft-lbs) and noticed the same sensation. I thought I made several turns of the rearward plug before the click but only half to a full turn of the forward plug before the click.

I don't want to put the car on the road and have the forward plug blow out on me.

Possibilities??

> Did I cross thread the forward plug despite my precautions to thread by hand followed by extension/socket followed by torque wrench?

> Is there a build up of carbon/goup on the threads in the head? What would I do to resolve that?

> Could this be normal since I did not use any antiseize (mixed reviews).

I am probably going to remove the forward plug tomorrow and replace with another to have a better look in the hole. Reason for the new plug is one-time-use crush washer.

Thoughts would be appreciated before I dive back in tomorrow morning.

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1982 300D-T (sold)
1988 300E (sold)
1994 E320 Wagon (sold)
1995 E320
1998 E300D-T
1999 E3204M Wagon
2001 E320
2005 E320 CDI