OK, so I tested the three front plugs with a spark plug tester, and they check out. I still need to test the rears, but first need to dig the wires out... you need to remove the coils and the ICM and the coil mount etc. to get at them, which is a pain.

I would have done it today, but I ran into another interesting test in which you slip a short length of vacuum hose over each of the coil towers and connect the wires to those, leaving a sliver of the coil tower showing under the vacuum hose. Then, you use a test light to short out one coil tower at a time. If a shorted coil tower does not produce a change in RPMs, that cylinder is misfiring.

First time I did the test, It seemed crystal-clear: all cylinders resulted in a drop in RPMs except cylinder #6, which created no change in idle. Ah-ha! I found the problem cylinder!

...no, wait, I had just forgotten to plug that plug wire back in after running the spark plug tester on it. Brilliant.

I tried the test again after plugging in #6, and all cylinders gave a more-a-less equal drop in revs. Then I realized that the engine wasn't misfiring at that point, and that of course all the cylinders would check out... the misfire then kicked up, so I quickly did the test again, and would say the cylinder fed by the coil tower furthest to right seemed (perhaps) a little suspect, but the misfire abated as I was still testing cylinders, so I can't say for sure whether it was that cylinder or another cylinder.

Today, I'm going to drive around the block, then chock the rear wheels and have my sister sit in the car and put it in reverse in an attempt to force the misfire -- the misfire is generally the worst ~2 minutes after startup when the car is in gear.

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"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."