Well, I found the problem. In the immortal words of Sherlock Holmes, "When you have eliminated the impossible, what remains, however improbable, must be the truth."

I went over pretty much everything. Checked the cam timing. Checked the timing mark on the harmonic balancer (a screwdriver against the piston top does not lie). Checked all the wiring to the ICU for continuity and shorts. Pulled out the ICU and plugged it into another car. (I have 2 Volvos with identical engines. Glutton for punishment, I guess.) Worked fine. (Oh, I replaced cap, rotor, and wiring near the beginning of this exercise.)

Finally, when the only thing left was the distributor, I pulled it out. Pulled off the rotor and internal cover and found the hall sensor flopping around loose! It had popped out of the mounting holes and the timing wheel had carried it along to one side. There it was scraping along under the timing wheel, still dutifully transmitting its signals.

Why? Because some schmuck had replaced the hall sensor and couldn't be bothered with setting the rivets! Instead, he simply epoxied the thing in! Not even good epoxy, but the 5 minute clear stuff. I'd like to wring someone's neck... Aarghh.

Anyway, thanx again for all the advice and pointers. Sometimes you get one that's off the curve.

- Andy