Trouble starting '98 SL2

[Louis Hom]

Last night, as I pulled out of the parking lot, my RPMs dropped below 1000
(no response to the gas pedal), then the engine cut out. I tried a couple
of times to restart, but it just cranked without catching. I threw it
into neutral so I could coast backwards off to the side of the road, and
then it started up (transmisison in Park) when I tried again.

This morning, I got into the car and it would just crank but not turn
over. Trying to put down the pedal before/during starting didn't seem to
do anything. I had to run for the bus, so I didn't have any time to
troubleshoot (can't even remember if the SES light was on), but at this
point I can't even get it started to get it to a mechanic. Any
suggestions would be welcome.

Relevant and irrelevant facts:
'98 SL2 automatic, 66K miles

Two days ago I took it into a shop that I trust because I mistakenly
thought I needed new brake pads (turns out I was hearing squeaks from
metal in the pads, I guess)

Battery reads a little over 12 V

I have noticed a gradual decrease in MPG over recent months, from about 28
to about 20, and I have noticed a new rumble/sputter on maybe the left
side of the car.

Alternator and battery were replaced about 2 years ago.

I replaced the oxygen sensor and plugs and wires last year.

I run a tank with B-12 chemtool about once or twice a year.

 

[Blah blah]

Last night, as I pulled out of the parking lot, my RPMs dropped below 1000
(no response to the gas pedal), then the engine cut out. I tried a couple
of times to restart, but it just cranked without catching. I threw it
into neutral so I could coast backwards off to the side of the road, and
then it started up (transmisison in Park) when I tried again.

This morning, I got into the car and it would just crank but not turn
over. Trying to put down the pedal before/during starting didn't seem to
do anything. I had to run for the bus, so I didn't have any time to
troubleshoot (can't even remember if the SES light was on), but at this
point I can't even get it started to get it to a mechanic. Any
suggestions would be welcome.

I thought cranking and turning over were the same thing. You need to
check for 3 basics. Air, fuel, and spark. I'm leaning towards Fuel as
being the issue. Clogged fuel filters from never being changed or
running your tank below 1/4 can cause damage to the fuel pump and those
2 things people commonly do.