mine was acting up during the summer. the 93's do seem to act in unison don't they? it was stubborn too - resisting a couple of cleanings. i had even put some other type of lubricant on it - didn't work. the silicone one i got from RS did the trick though and it hasn't acted up since.
1993 300e-2.8 - gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"