91 chevy g 20 has no power wont idle

91 chevy g20 new engine 3000 miles ago ran great for a while left van idling for 30 min came out and van was dead now i have no power can barley keep it running in park no codes cap rotor plugs and wires are new just cut off cat thinking it was pluged no help

91 chevy g20 new engine 3000 miles ago ran great for a while left van idling for 30 min came out and van was dead now i have no power can barley keep it running in park no codes cap rotor plugs and wires are new just cut off cat thinking it was pluged no help

What engine?
First test is.
Are you losing spark or fuel pressure when it acts up.
Is the gas tank empty?
Fuel filter good?
What is fuel pressure reading?
Got good hot blue spark from coil and to all plugs?
Lot of PCM circuit board shorts on them years.
Have you give it the old tap/twist test?

5.7L, ignition new at install of engine, fuel pressure good, spray pattern from both injectors good, when i try to rev up in park it bogs out even while i spray carb cleaner, i am thinking icm or pcm but i have had same problem with caprice of same year and engine and never fixed problem for more than a cupple of weeks/months at a time. i am a certified master tech and i dont know why but 91 chevys w/ 5.7 get me sometimes

5.7L, ignition new at install of engine, fuel pressure good, spray pattern from both injectors good, when i try to rev up in park it bogs out even while i spray carb cleaner, i am thinking icm or pcm but i have had same problem with caprice of same year and engine and never fixed problem for more than a cupple of weeks/months at a time. i am a certified master tech and i dont know why but 91 chevys w/ 5.7 get me sometimes
91 is the old breed between older and new.
They just have different bad habbits.
Like pick upcoil and ign module and shorted boad on pcm.
Good hot blue spark to all plugs.
Give the pcm the old tap twist test.