how many miles on the filter, 10k, 50, 250k? maintenance history?
looks are great but smack it see what falls out.
last one i saw that looked clean , was full of volcanic ash (white dust finer than flour).
next time it doesn't start:
1: check for flooding (look at plugs for soaked with gas on tip, and or floor it and start it)
2: check for spark.?
3: look down TB to see if the injector is squirting when cranked.?
(works on ALL 8v KICKS)
if car wont start with gas and spark. it is flooding, you should be able to smell that.
I guess you are saying it starts one day and not the next.
The engine runs ok when it runs is the implication here. no shake when idling.
so I will ignore , compression tests, and vacuum tests.
but any old 89 , needs that done , just to see the general condition of the engine.
150psi on each cycl. and solid 19 inches HG (HG= Latin for Mercury) on vacu. gauge.
attach vac gauge to EVAP nipple.
do compression with coil (primary ,not secondary HV plug pulled)
deactivating the coil .
I have a compression page. if you click my link.
Intermittent's must be trouble shot when they happen. (if it is not broke cant fix it , yah?)
it could be anything.
spark , fuel or ECU.
if really unlucky , you can have a problem with start up air.
there are 5 paths of air to start an old 8v. can be fun to sort that all out.
fresh-air for start and idle
or gosh forbid.
the Fuel pressure regulator stuck closed and fuel pressure is on the moon.
EFI is complex, not all problems are simple.