Engine Performance problem
1991 BMW 525 6 cyl Two Wheel Drive Automatic 249584 miles
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car cold starts fine runs about ten mins then erridic idle then dies,have to leave key off five mins or so then same deal help please

I would initially suspect the coolant temperature sensor as the possible issue here. Is the check engine lamp on?

possibly go to a salvage yard & get a used electronic ignition module (as new ones are not returnable & quite expensive) see if this cures the problem.