Less expensive than a $500 ECM, Buick4Fun. Plus about $300 labor. 
The dealerās mechanics said they would have tried borrowing a computer if they had one, but itās very rare that works out. Thereās a core charge, so most used ones are returned to the manufacturer. And once the shrinkwrap is broken, thatās it. No returns. But I did look high and low online. Good thought.
(Hey, weāre popular!)
I am going to spend some time on the phone with some indie mechanics tomorrow. Thanks to all again for your interest and suggestionsāIām noting them all. Iāll let you know if I get any more clues.)
I myself have been dispatched Chevrolet Luminas (year model 1999) that were brought in on the hook (tow truck) and you go to the lot with the car pusher and a friend and the car starts right up and you drive it in set it on the rack turn it off and try a restart and it just cranks,will not start.
I would not take any other action before a new fuel pump JMHO.
jennifer,
i was working on a buick lesabre and it wasnāt running right i went online and found this forum about your car. your car sounds like the one i was working on but you hadnāt solved yours either,I had done or tryed all the things everyone was talking about in the advice they were giving you and the car still didnāt run correctly. I worked three days on it and noticed that if you left the key in the run position and tryed to start it again it wouldnāt start (ever). But if you cycled the key off and tryed to restart the engine would start. I noticed on my scan tool that engine speed(crank sensor), mass airflow and injector pulse width were all frozen with the engine speed at 20 rpm. If you cycled the key and tryed to restart the engine run and all the parameters for the sensors would be normal until the engine died and then it would do it all over again. By turnign the key off and on you are putting modules asleep and then waking them up. So knowing that I assumed that the ECM (engine computer) was messing up because of the three things freezing up. So I bought one from the junk yard ($25) and the car runs correctly. This is what worked for me, I hope you find it helpful and hope its of some use. Good luck.
A bad airflow sensor would generate a code.
I had a similar problem with an Olds Intrigue, would die randomly and almost always restart instantly. I got so I could throw it into neutral and restart it and slip it back into drive without missing a beat. Problem persisted for 2 years until I noticed the ground cable from the battery was only about 6 inches long and secured to the fender with a 10 mm bolt right under the battery. Problem solved when I got a longer ground cable and ran it to a bolt on the engine block.
You need a volt-ohm meeter. It will tell you the current draw (amperage) as well.
i have a 1994 buick lesabre no computer codes just looked real good all around the engine compartment one of the wires to the O2 sensor was loose on the sensor went to junk yard $2 auto zone $60 never had another problem
I have seen a bad injector with low resistance cause issues with the injector drivers. You can test pattern and volume and be good. Check resistance. Low ohms = high current, ecm may have problems intermittenly. Iāve seen it , it happens. Was a 90 Buick.