Baffling, intermittent hard to start issue

93 Tercel (in top restored condition) cranks but it is slow to catch occasionally.

The vehicle has 230K miles now. I plan to take it to 400K and it has:
-New fuel pump,
-Oil filter is lifetime but has been replaced at 150K
-New Fuel injectors,
-New Fuel pressure regulator,
-Cleaned/decarboned throttle body and Air-Idle-Control valve
-New distributor entirely (including the cap)
-New plugs,
-New Ignition-control module,
-New master-vacuum sensor,
-Checked vacuum hoses
-New Idle-control vacuum sensors
-New water-temp sensors (all four sensors around the thermostat are replaced)
-New valve stem seals (that was an expensive repair two years ago 210K)
-Timing and advance are properly set

The problem is still there. After sitting for a few hours, the vehicle cranks, catches and straggles for a second before recovering and running fine and smooth.
For the life of me, there is nothing left I can think of. It's as if a gremlin lives inside the cylinders and spray-paints the spark plugs while I am gone just to mess with me. Is it a fuel leak? am I loosing fuel pressure ? (there is no smell anywhere) HEEEEELP :-)

Comments (3)
No. 1-3
ThomasAn
ThomasAn

Scotty, here is the result: 150/160, 80/90, 80/90, 95/110

My theory is this: This engine was maintained well (all maintenance done and oil changes every 2500miles since the beginning), but these engines are known to get bad valve stem seals no matter how well maintained. I had the valve seals replaced two years ago at 200,000miles, but I don't think the dealer mechanic cleaned the valves at all, he managed to replace the seals from the top without taking the head off. There must be a lot of oil deposits on the valves by now and they may not be closing properly.

Should I apply CRC a few times ? Would that work in this case ?

ThomasAn
ThomasAn

Roger that. Will do. Thanks Scotty !

ScottyKilmer
ScottyKilmer

Editor

do a wet and dry compression to test the engine strength first