Are you aying that 3 or more mechanics duplicated this condition,were allowed to spend, lets say one hour looking the car over and not one had any idea what was wrong? In my day letting a car with a sympton that was both so significant and easily duplicated get away from you not repaired was cause to hang you head in shame.
I can’t imagine this happening. I have worked for people who would have fired me on the spot if I was not able to present a list of items that I had ruled out as being the cause of this condition.
I can only attenuate my exasperation by relating that the car is an 1988 and perhaps all 3+ mechanics are used to having more help with the diagnosis. It is a shame these guys gave up so easily.