i have experienced this problem the past day or 2 now. whenever the car is warm and been and i park the car i can start it up right after turning off the car and it will start right up. Now if i let it sit for a little while say 10-15 mins or more and go to start it up it will start up normally then when the idle drops back down it starts to stumble and sputter and almost die but it doesnt. verying from 750rpms(warm idle) to about 250rpms and almost stalls out. if you give it gas it will rev up smooth though, even during this hic-up. i have cleaned the air filter, changed the fuel filter, the main relay isnt the problem because you can hear the fuel pump kick on and hear the main relay click(check engine light does not stay on either). So im kinda stumped Im thinking it could be the fuel setup, either the fuel pressure bleeding off or the injectors bleeding fuel into the motor causing it to flood, or a vac/manifold leak. the plugs wires fuel filter and air filter have either been changed or cleaned.

what does everyone think it could be btw its a 91 teg ls

 

I had this same problem i could not figure it out for the longest time i changed my injector O rings and that solved it. good luck.

 

ill try that first. im also going to redo the vacuum lines. before i cleaned the air filter and fuel filter when this happened it would just kill the car.