I was given advice to take the air filter off and crank the car over.  Watch to see if there is fuel spraying from the injector.  I had almost nothing spraying out on mine.  There is a relay box in the engine bay that I had to pop apart and found a solder joint was bad.  I resoldered it and haven't had trouble since.  In the image the relay is at the upper left with a white ziptie around it.

My issue was generally for warm starts.  I had some sputtering issues while driving and a local member recommended changing the oil (auto trans).  That fixed that issue.

Did you replace the O2 sensor? There is a very inexpensive Bosch universal that works.

Vacuum hoses are the weakest link in SPIs there is a kit to replace them. Watch this! https://www.youtube.com/watch?v=hBJ7k-1bYxQ

Check the various sensor vacuum hoses and elbows for breaks.

No mention of injector work... are you seeing and getting a good fuel spray when running and mORE down the throttle body when you give it the beans?  Can be seen with the air filter housing off.

  Simply a guess. but if you have some good fuel pressure at the throttle body i would be skeptical of the injector spitting enough fuel for it to run. even worse under load.

Good Luck

Never mind I think that SPI is fuel injection.

Accelerator pump?

Hello everyone! So me and my pops have a 91’ spi mini that we just cannot figure out. I’m a GM technician so I’ve got a good bit of mechanical know how but we can’t seem to figure this thing out. Mini will not start on its own without either. Even with either you’ve still gotta stay in the gas a bit to keep it running. Once running it spits and spudders under acceleration, and backfires on decel. Oh and even better it likes to randomly shut off at stops or when you let off the throttle. Warm or cold it almost always needs either to start. So far we’ve replaced all vac lines, checked fuel trap, replaced fuse block and all fuses, ensured fuel pump is operation and filters are new, new spark plugs and wires, and a few other things. Seems like we can’t seem to diagnose it to save our lives. While running we’ve tried disconnecting ect sensor, tps/app sensor at accelerator pedal, o2 sensor, and various other sensors. None seem to have an effect on way it runs. Almost like we’re flying blind. Also tried some gm top engine cleaner in thoughts maybe we had some bad fuel. No dice. Any and all advice would be greatly appreciated.