IACV? How do I go about checking that?

Yes, I have enough fuel, 1/2 a tank of 92 octane just before this happened.

Also, how do I go about checking the timing?

I don't believe anyone messed w/ the fuel mixture, however I had a guy get a sticker on the car about 2 weeks before this happened. I'm pretty sure it has nothing to do with the issue, but problems really started one day when I was on a long voyage and the coolant light came on (rad needed to be changed anyways). Since then, this problem materialized. Initially, the problem was just a rough idle that got progressively worst, then developed into a no-start scenario over a period of about 4 days - a week.

I know spark is reaching the spark plugs, because I pulled a spark plug out and plugged it in, ground it against the block and cranked the engine - plenty of spark came out. This is how I originally diagnosed the distributor rotor/cap issue.

Is there ever a case of the electrical components needing to reset, or are these relays pretty much plug and play?

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87 300E
202k on the clock