1983 380 SEL - Stalls frequently, but not always when I come to stop, although RPM seems set right (is electronic controlled), 6-700 in P or N and 5-600 in gear.

Problem started on first wet day after I had reconnected a loose 3 conductor canon plug that sits in a bracket between coil and front left headlight. When not connected, engine idles 1-200 RPM faster and does not stall.

Any clue as to what this plug connects to and why being connected causes this problem?

I note emission controls tie to RPM, temperature and oil sensors. Also have not been able to get electrical fan to operate. It works when hot-wired to battery, but never comes on even at high engine temps. fuse is OK. Could this be related to idle problem?