Yes, the resistor in the rotor is a very good idea. Not because it would be intermittent, but when it opens, the spark has to jump across that additional air gap, and that makes everything ignition-wise marginal. And while cranking, that's when you need it to be reliable, not marginal.

That was one of the very first Volvo fixes I had to do. My daughter's 83 -- our first Volvo -- was a no-start because of that rotor. I had just brought home our second Volvo and her car was just two blocks up the street, so I snagged the rotor from one to put in the other. I think the good one measured about 1K ohm between contacts. The bad one, infinite. Anyway, it is far easier suggestion to try that first if you can.

Of all people, I should not assume ignition suspects start out with new cap, rotor, wires, and plugs. That's what they call a tune-up these days, I hear.
--
Art Benstein near Baltimore

Shirts get dirty. Underwear gets dirty. Pants? Pants never get dirty, and you can wear them forever.