As you know, I also have a 85' 380SE. You may also know I was having a stalling problem, but mainly when placed in gear, when the engine is fully warmed up, but there have been three occasions within 3 months when it stalled while stopping. Once was when I came to a stop to make a right turn. It started right back up and went on. The other time was when I stopped at a traffic light. When it was upshifting, the idle was going down too far and at the end, it stalled. The other time was last week when I was turning into a parking space at the supermarket. It was a sharp left turn (as I was swinging back up toward the other direction), and like you described, the steering became heavy and I noticed the engine had stalled out, but I went ahead and coasted into the space. It has not stalled out since, nor has it stalled when placed in gear, BUT over the past few days (since last Tuesday), temperatures have only been in the 50s, so the engine is running cooler, hence the decline in stalling.

I am wondering if we may not have the same problem- whatever it may be.
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1985 380SE - 265K miles!