Starts fine (cold)no spark after warms up - 1992 Mazda MX-3

toy 4afe engine.
warm no starts.
so did you check for spark loss , warm? or hot?
if not why not?
if spark is good, did you use test fuel to see if added fuel starts it?
are the the spark plug tips (yes,look) soaking in gas (failed) or dry.?
this is how you diagnois all Gas engines. even a lawn mower.

ever do the 60k lash check on valves?
put in a new timng belt, may be yours slipped, its a 60k service.
do the lash checks at 60K,
if lash is too tight, the gap can go to zero hot,killing compression
Valve clearance (engine cold), (in.):
Intake (0.006) 6 thou
Exhaust (0.014) 14 thou.
why not do the FULL 60k tuneup now. not cutting corners or skips
and win.

is the CEL out , hot driving>
the check engine light.??

run fault codes and come back in the comment box

ever tune it up, try new spark plugs. gapped to spec.
starts fine and runs fine, not said the latter....????

Cold starts are the hardest, takes
these things to start good. cold.
1: go winter fuel (if cold out, isit? then winter fuel works best)
2: a good engine and good spark plugs, (hot spark)
3: good cold start fueling,
to get #3 the modern car 89- now. needs a working and accurate
ECT sensor, this tells the ECU exactly how much fuel to use.
if the ECT reads warming than REALITY, the fueling will be weak
and may not start or stall fast.

no location stated, nor if car is a daily driver, that is fresh fuel
every week,,,,

Have you checked the fuel pressure regulator to see if its leaking?

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

4.3L V6 CPI - center port fuel injection . you need 62 psi .When cold give it a shot of carb.cleaner or starting fluid ! does it start then ?

415-455 kPa (60-66 psi

Check your battery cables,make sure there tight and no crode,

check spark plug gaps ,should be 25th if too wide it will have a problem starting when cold

Not to put firestone down but how intricate was this diagnostic that they preformed? It sounds like they just plugged into the OBD2 port and looked for any codes in the history.
You may be right, it may have to do with temperature. But I'm thinking more in the respect of a faulty sensor that is changing with temperature. That is, if it has to do with that.
The other thing is the fuel-pump. Has it been tested?
If possible, When this no start situation occurs, investigate it. Find out if you have a no-spark or no-fuel situation.

Make sure all the glow plugs are working.

delta connection is not proper it has been loosely connected so check the delta connection else change the spark plug if there is any problem in spark plug