trooper won't hold idle

93 isuzu trooper dohc, with 78k miles, which starts immediately but stalls
immediately.

about one year ago, it would run erratically and once a new fuel pressure regulator
and idle air control sensor was installed, all was well again. fuel filter has been
replaced. once engine warms up, it runs fairly stable for a while but can stall out
when coming to a stop at traffic light when transmission downshifts

this just started happening couple days ago and on the first day when it happened it
had been running absolutely normal the day before. once the problem with stalling
happened upon startup, had to keep one foot on accelerator and keep rpm's up around 1k
to 2k and a large amount of sooty water came from tailpipe. fuel tank was full so am
not sure if there's a connection.

about 6 months ago, the catalytic converted was replaced, new coils, new EGR, new
plugs, new harness

as far as I know, it could only be fuel pump, fuel pressure regulator or mass air flow
sensor. the fuel pump seems ruled out since it runs normally at least for a while once
warm, the FPR seems ruled out since it's only one year old and the trooper 93 does not
have a MAF sensor connected near the air filter

on the other hand, the FPR could be a bad part needing yet another replacement

I suspect either the fuel pump and maybe it gets enough pressure when warm
to run normally (or nearly so), or else the evaporative loss canister (aka
the charcoal canister). You can test that by disconnecting it for a few
days and see if the problem goes away.

"Thomas" <th DeleteThis @m.as> wrote in message
news:5ae02iF2mfonrU1@mid.individual.net...
> 93 isuzu trooper dohc, with 78k miles, which starts immediately but stalls
> immediately.
>
> about one year ago, it would run erratically and once a new fuel pressure
> regulator and idle air control sensor was installed, all was well again.
> fuel filter has been replaced. once engine warms up, it runs fairly stable
> for a while but can stall out when coming to a stop at traffic light when
> transmission downshifts
>
> this just started happening couple days ago and on the first day when it
> happened it had been running absolutely normal the day before. once the
> problem with stalling happened upon startup, had to keep one foot on
> accelerator and keep rpm's up around 1k to 2k and a large amount of sooty
> water came from tailpipe. fuel tank was full so am not sure if there's a
> connection.
>
> about 6 months ago, the catalytic converted was replaced, new coils, new
> EGR, new plugs, new harness
>
> as far as I know, it could only be fuel pump, fuel pressure regulator or
> mass air flow sensor. the fuel pump seems ruled out since it runs normally
> at least for a while once warm, the FPR seems ruled out since it's only
> one year old and the trooper 93 does not have a MAF sensor connected near
> the air filter
>
> on the other hand, the FPR could be a bad part needing yet another
> replacement