Update: replaced with the new wires and something still wasn't right - still an occasional, intermittent misfire when cold (though nothing bad enough to stall the car anymore and definitely WAY better with the newer wires). I suspected the coil, so I purchased one locally but mentioned to the seller that I *may* return the coil if I end up not needing it. I tested resistance on the new coil, and it checked out, well within specs. I then checked my old coil and it too checked out well within specs. So I ruled the coil out.

I decided to pull the plugs. They will probably need replacing. #1 had some deposits on it. I couldn't tell if it was carbon or oil since it was very light. Could be the beginnings of valve stem seal wear. Either way, not enough to worry about for now. I regapped the plugs at .030 for now (I know they should be between .032 and .040) and reinstalled.

In plugging the wires back in, I made a startling discovery. Apparently on this new set of wires, the 2nd detent is VERY hard to click in. You have to grasp the resistor end with both hands and push with all your body weight to get it to snap into place. I realized none of the ends was snapped in properly, although when I first installed them it "felt" like they were all the way in. After snapping each one in all the way, the idle is now 99% misfire free. I believe the remaining 1% will be corrected by new plugs.

Fred, glad to hear you are sorting your issues out.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280