74 1.8 - fuel pressure regulator?, opinions. Options

[wonkipop]

car = 74 1.8 L jet (all intact).

problem =
out driving this morning - gradual then worse loss of power. no accelerator response.
pulled over. cut out. no idle. let it sit for a few minutes. restarted it. got it going.
got up road all right, but symptoms kept coming back, then going away. limped it home.
fun ruined for driving, but fun diagnosing started.

felt like your classic fuel starvation.

background. car has been recommissioned and back on road for about 5 months.
running beautifully.
fuel system entirely rebuilt. clean tank. new fuel lines. new fuel pump. new injectors.
all vacuum lines renewed. all ignition compenents renewed. except coil (which could be original, looks like it, but coil was tested and was a goody).

one thing = fuel smell in engine bay on lhs around air cleaner. comes after a few days sitting. had put this down to saturated charcoal cannister, feeding back fumes into aircleaner. have inspected all fuel lines etc thoroughly and no signs of any external fuel leaks/wetness. just a vapour smell thats not there all the time, just after sitting.

pulled everything apart today down there after getting home today.
checked everything. all tight, no air leaks. no bad hoses.

looked at pressure regulator. which sits right there under aircleaner.
i have no reason to think its not original and about 45+ years old.
and did not get replaced. looks great externally, but.........internally?

will get car into shop this week. where i can get some guages on it etc.
at home with car. nothing but basic tools.

but whats thoughts out there.
anyone had this one before.

[wonkipop]

calling mr. perrine / or any 1.8 guru.

@ClayPerrine

i've been able to induce the fault, got a pattern.

start car cold and it as it warms up it comes up to steady idle and stays stable.
car revs cleanly, drives cleanly.

switch off when hot and leave it for a certain amount of time, roughly 10-15 minutes and it restarts in idle hunting mode, 500-850 rpm up and down and won't come out of it.

i tripped over this yesterday when i was going over every vacuum line and square inch of intake plenum, intake boot etc. it started happily and idled away happily for 15 maybe 20 minutes while i was checking for leaks. i switched off to make a coffee and take a break, about 5 minutes. restarted it and it went into hunting mode for maybe a minute, then settled down to steady idle. thought - interesting! - so switched off and left it for just over 10 minutes and when restarted it went into idle hunting idle mode and would not come out.

left it for around 6 hours and started it before going to bed. started up fine from stone cold and settled into steady idle. let it run for 10 minutes or more until it got warm. stayed steady. turned it off.

today i managed to repeat the fault induced yesterday with the same pattern.
started cold fine and came up to steady idle and sat happily. switched off and immediate restart, idled happily. switched off and left for 5 minutes, started with a stumble and about i minute or less of hunting and then settled into idle, could not induce any misbehaviour by some revs etc. turned off and left for 15 minutes and restarted it went into hunting idle mode and would not come out of it.

figure i should go into component testing mode next. sensors etc?

have eliminated, fuel pressure, timing, points, spark and i believe any vacuum leaks as causes.

on off chance anyone has struck this before any pointers might help.

its pointing to some mixture problem at idle and possibly under power, but i haven't been able to make the under power situation occur, did not take it out for a drive after inducing hunting idle.

realised i might have had this problem for a while but not noticed as particular behaviour makes it happen. starting it after a certain period of time has elapsed after hot shutdown and before its gone cold again. been just driving it for the last couple of months with a start up and early morning drive once a week where i don't switch it off - just drive it, have fun and park it back home. what i had done last sunday was take the car out, but i left it in the street for about 10 minutes between getting it out and going for a spin. the fault emerged soon after i was down the road after the restart.