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
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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.

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Ed H. wrote:

after reading some notes via google, I replaced the idle air control and all is fine
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Great!

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wrote:

Is that the thing that the air hose from the fuel pressure regulator runs to (2001 trooper 3.5)? ~GJ~
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Is there one of these on a 2001 trooper w/ 3.5 engine? ~GJ~
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Gemini Jackson wrote:

normally immediately on throttle body, ask the local parts shop to show you an image of the part (Napa has it online) and buy one from Napa or Autozone if you can visually see same part on throttle (look at their image first on store computer)
if you have one, it's just two small bolts and about 1 minute to replace it, no special tools needed
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