I've been reading older posts and have a lot to think about, but it's dark so it has to wait. Some history:
1985 W123 300D Turbodiesel, 176K miles. I've had it for two weeks. One test I did was locking the front drivers door and all 4 doors locked and unlocked fine. Engine cut-off was instant. Until today. Today I locked the doors using the key. I think all 4 pulled down and know for sure the driver and passenger side locked. And unlocked fine. Later that same day, I went to lock with the key again but this time I know only the front door and passenger side locked, the back doors both stayed unlocked. Bigger surprise to follow, went to shut down engine but it kept running for about 10~15 seconds then shut down.

Yesteday I was under the hood with a vacuum cleaner/blower getting rid of debris and clearing the drains near the hinges. I was careful not to get near the vacuum lines (I think). I've checked the connectors quickly but can't find an obvious disco'd line or anything.
Basic questionis what could I have touched that would affect both the locks and engine cut off at the same time? I've cut n pasted a whole raft of stuff from this site and will tackle my problems but a quick diagnosis would save me from freezing my tired old butt off. Any good accurate CD Manuals for the 85? I see it's a lot different than my old 83's.
Thanks Much. I Promise to report back when fixed :-)

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1985 300D 197K - Semi-Daily Driver Diesel
1998 Volvo V70 AWD 226K - Daily Driver 2
1998 Volvo S70 140K - Wife's DD
2003 GMC Sonoma ZR2 Option - Rusty Truck
THE BABY 1958 220S Sedan 66K All original, never restored and never will be.

For the most part, a vacuum leak anywhere can affect vacuum-operated items everywhere. If your engine is slow to shut down with the doors unlocked but not locked, you probably have a leak in the "unlock" circuit.