Here's an update to my Wednesday post which said:
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My daughter came in from school today telling me her '91 240 (188K) stalled on her twice today, once after a hard stop and once during an accel after idling at a traffic light. She also said the car had developed a noticeable shake. Its been stalling occasionally for months but the shake is new. I had been thinking the speed sensor needed replacement, but now . . .

After driving around the block, I'm thinking its got a cylinder missing. There seems to be a gasoline smell from the exhaust, but it might just be me. What would be the order of the things that I should check out, etc. There's no check engine light.

Recent repairs: coolant temp sensor, AMM, motor mounts
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Tonight I installed a new fuel pressure regulator, distributor cap and rotor, and also pulled the plugs for a visual (no oily wet plugs - good). I also confirmed the firing order.

I'm back to suspecting the impulse sensor - doesn't it directly effect the timing? My Chilton's said I could check it by measuring the resistance between terminal 10 and 23 on the ECU connector. I tried this but I'm not sure I'm locating the right terminals.

These steps haven't stopped the engine shaking at idle. Doesn't seem to have much power either . This is no small shake -- I estimate about a three-quarter inch amplitude. What can cause this thing to shake that much? I'm open to suggestions.