dpb wrote in :

On 2/4/2014 6:36 PM, Doug Miller wrote:
...

... I'd go the extra
step and actually check the plugs themselves, not just the spare.

I'll do that tomorrow morning and post the results.

Is this the carb-injected or fully injected arrangement?

Fully injected.

Have you tried a squirt of starter fluid while cranking?

Yes, and got a very impressive backfire through the throttle body.

OK, it's next morning; I didn't get back last night.

The others are basically correct imo, too, you're timing is screwed up.
You've demonstrated spark to my satisfaction; if there is a plug issue
it'll be sufficiently minor to be dealt with later if it's still running
a little badly; not that they're not firing so skip ignition issues.

Either you have swapped firing order w/ the plug wires

Definitely not. I've checked that about five times now.

or you've slipped a timing belt cog or the like...

Saturn S-series engines use timing chains, not belts. I suppose if the tensioner broke, the
chain might have jumped... but that seems unlikely.

Not sure about the sensors on that engine whether it's possible to get a
polarity problem or otherwise screw up the indicated position while the
mechanical is ok or not...

Saw pretty much the same behavior on our other Saturn S-series last summer when the
crankshaft position sensor failed. That tests good on this one, though.