Weak coil current ramping on DIS Waste Spark system is monitored by the HFM-N3/4 module...if a coil is weak, it usually shows up at Pin 8 as a code 21/22/23 , specifiying each coil set.

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A Dalton

Our 93 300E 3.2L did this, the solution was new spark plugs and the connectors (3) under each coil. Had read many posts and it was often suggested to just change them (Thank you Mr. Dalton!) so I did and the problem was gone!

One of the connectors had a very faint ash gray color where the black rubber ended at the ceramic on the plug. Also the plug had a tan/brown spot on the insulator that the other five did not. Hope this helps.

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Good observation..that is the first tell-tale sign of failure on those coil to plug connectors...................

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A Dalton

Also had that problem before and I change them what I remember the symptom was slight difference but I will check them out today.

My thoughts is like this, I don't notice anything in the winter time or almost no problem under 0 degress.
Only in hot weather so the problem would not be running low on fuel (in the winter the car needs more fuel so I guess the car would perform worse)

rather rich on fuel or air leak downstream from airmass sensor but I can't find any air leak is there any throttle position sensor that could be the problem?
Car is starting up fine in all weather no problem in idle.
Will post when I fix the problem unless it's get's to expensive.