Some guesses?

[jeffcoslacker]

Only happened once, been fine since.

Some background, so you have all the pieces. 1997 Lumina LS, 3.1, 140,000 miles. Last week I put 1000 miles highway on it. I pushed the fuel as far as possible, came home very close to dead empty. It was quite cold, and I didn't feel like pumping gas.

I was so low, that I went and got 5 gallons in a known-clean gas can and put that in before attempting to drive it the next day. It ran fine.

The day after that, I put 5 gallons in at the gas station. When I pulled out I got on it hard because you have to pull out with a blind hill to the left, and many have gotten creamed there, so I don't mess around coming out of there...

But the light that usually never changes red (fire station signal) turned red suddenly, and I had to haul it down to a ABS-activating stop (salt on the road)...and right away it had a dead miss...one cylinder, felt like, not that hard two cylinder miss like a coilpack does...

I put it in neutral and revved the motor, it felt fine except at idle, and when I took off there was no loss of power...at the next light and ever since, the idle has been rock steady and smooth, as usual.

No CEL, despite that it obviously misfired on one hole (rythmic, steady miss) for at least 30-45 seconds.

My best guess is that the EGR stuck open slightly when I dropped the throttle, and created a lean miss in the closest cylinder to the passage.

I thought of a few other possibilities, but rejected them.

You are welcome to propose your own theories. If it happens again and a cause is found, the winner gets absolutely nothing

[GreyZ34]

Well I have this happen often on my 95 Monte can remember about the 3.1 but at the back of the engine is large vacuum hose mine would slip off after hard braking and I would have to put it back on. It would back fire in the FI system trying to start it and it was miss badly at idle. Complete loss of power over all as well.

[Blue Bowtie]

How is the oil level? Was there any noticeable smoke while it was running rough?

I'm thinking that a high-G stop like that may have slung all the sump oil forward starving the pickup slightly, perhaps starving the lifters, and possibly forcing a little extra oil on the 2-4-6 cylinder walls. That may have temporarily caused a bit of oil fouling on the front holes.

Just a WAG.

If all your hoses, electrical connectors, and the throttle body is securely mounted, it either starved for fuel on hard decel or slugged the cylinders with oil.

[jeffcoslacker]

No smoke...never has. Tight little engine, uses .5 qt between oil changes, same as when it was new.

I may change the fuel filter...I've come close to running it out of gas a few times since changing it last, about 30,000 miles ago...

I took a look at all my vacuum hoses, found nothing wrong. The PCV valve was about half unseated in the grommet....I suppose it could have lifted up and was sucking air?