Wow. If the big connector was so loose that you could actually see it lifting off the ECU, that would definitely give you some unexplained driveability issues. OTOH, it's a cheap fix, and that's a very good thing. It's a practical reminder to us all to first check that all electrical connections are well-seated.

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't