'90 Century Engine turns off in motion

[chobart]

I have a 1990 Buick Century Wagon. I was cruising on the highway when the engine lost power and the instrument panel came on. It lurched back on and I kept going. This repeated like 3 times. When I got home the car wouldn't start at all. An hour later it still wouldn't turn over.

The following day, it started right up and drove me a couple miles to where I was going. When I left the place, I was having trouble getting it going again. It would turn over once and shut down, or sometimes I could hold it going with the gas pedal, but when I let go it would stop, or when I put it in drive it would stop. I got it home by keeping the gas pedal down a little and dropping it into neutral at stop signs and braking with my left foot while I gave it gas.

As the engine spins to a stop I can hear friction - like a spinning grinding noise, not too loud but definitely there.

I recently changed the tranny in this thing and had to put in a compatible 3-speed TH tranny where the 4-speed was. One thing I just figured out is that I had the wrong dipstick sleeve on the tranny and I was running super low on Tranny fluid this whole time. I've also had some overheating issues.

When I try to start it in park, is there anything in the transmission that would be causing friction? I'm new to auto trannys so I don't really know. I know the torque converter must be spinning at least. Or should I be focusing on the engine? Is there something simpler I'm overlooking here? Would the car refuse to start just because it gets hot? Like a temp-sensor shutdown or something?

Any help would be so appreciated. I need to get to some job interviews so that I can make money to get another car!

[Tech II]

Did you do anything to the ECM/PROM, since you change the vehicle from a 4sp to a 3sp?

[chobart]

No I havent. The car ran well for about a month after the change, for what thats worth. I have tried disconnecting the electrical connector that is supposed to control the torque converter clutch and it ran the same.

[maxwedge]

Check the battery cables, especially the ground that may have taken off during the swap, hard to tell what is happening here, is the starter not cranking the negine?

[chobart]

I will check the cables in the morning. The starter cranks the engine fine. It seems like the hotter everything is, the worse it runs. Real hot, it just cranks. Let it cool a little and it will turn over once. A little cooler and it will start and run only if I give it gas, then shut down after 10 seconds or so, and if I leave it overnight, it starts up and runs and idles without touching the gas pedal.

[maxwedge]

Check the fuel pressure when this happens, also check spark, just basic diagnostics.