Thanks for all the replies. I went to two mechanics and spent the afternoon trying to fix this problem, and turns out this might be a simple problem. I'm saying MIGHT because the problem does reappear this morning.

Both mechanics did:
1. Feel the top hose, open the raditor cap, bleed the thermostate, and determined that cooling system is functioning fine. Cooling fans and Temperature gauge are working properly as well.
2. Found a vacuum line leak (the plastic valve connecting to the A/C duct vent is broken). They said this won't cause the engine shutdown, only less performance or efficiency.
3. Rev up the engine while the vehicle is parked. It stalled three times with the sympton described above at first mechanic, and none-for the second. The engine sounded fine to both mechanics.

Mechanics diagnostic:
1. Possibly a bad tank of gas with water or something in there, is causing the engine to shutdown sporadically. It'* the engine shutdown caused the HOT, VOLT, Oil Pressure lights to come up, not the other way around.
2. Second mechanic also mentioned possibly bad fuel pump, or faulty cam sensor (not sure if I said it right). Since car didn't stall, he would need more info, i.e. leave the car and he'll connect the computer and drive it around.
3. Probably not a cooling system problem or computer sensor problem, because Engine Check Light isn't on.

Action took:
1. Changed air filter $10, fuel filter $30. Vacuum line valve replaced $10.
2. Add a tank of Exxon 93 supreme gas with another bottle of Techron additive.

So far, car stalled only once, while accelerating quickly on the local street in operating temperature this morning. I will keep everyone updated on the situation.

After reading your latest, I have to say....

D'oh!! All three lights are on.
That means the key is on, but the engine isn't running. We were all looking at this the wrong way.

Now I will turn this over to the Gearheads in the crowd....

Looks like a minor misunderstanding. It was posted that when the hot light came on, the car stalled and then the other lights were on as well.

Once a stall happens..they will be on. However the mechanic was able to duplicate the problem and saw the stall before any of the lights.

Merely one of those times when the millisecond of which mght have been first..the stall or the overheat light.

Personally.... I don't think the pcm turns the car off for an overheat situation....I'll be looking at a book about that soon.

To an untrained person, it'* impossible to tell which happened first, the lights or engine stalled. From all the analysis, looks like the lights are on because of the engine stall. Some more stalls happened since yesterday. This morning the car stalled 20 yards from the house. This seems to agree with the impurity in the fuel tank theory. However, the car does stall once or twice during the day, typically when acceleration... so I don't know what'* going on. Maybe I will leave the car to the mechanics to hook it up to his computer over the weekend.

How much gas is in the tank? I grew up in Austin, so I know how humid it can get in Houston.

I'm beginning to suspect/believe that it could be moisture in the fuel do to condensation. Problem is, I don't remeber if you can get what we use up here to "de-ice" a fuel system down there. Maybe a good quality fuel system cleaner, and run out the gas you have now might help if that'* the case.

Left the car at the second mechanic and he drove it overnight:

1. First he said that computer is bad. He is getting ERROR on read out. I assume it'* ECM he is talking about. Repair is estimated at $300. Parts $220 + labor.
2. From his experience, if computer is bad, ignition module is probably bad too. So change it for another $200.
3. Possibly intake manifold coolant leak. Estimate $700 repair. I haven't talk to him about where he saw the leak, since we had bleed the thermostat housing couple times, I'm hoping he is seeing the leak somewhere around there.

My question:
1. Is it easy to change the ECM and ICM yourself?
2. Should I get these new from dealer, or auto parts store, or junk yard? If pulling it from junk yard, what do I have to know about different year/model or any 3800 VIN L will work? Anything else I need to know about ECM or ICM?

Again, thank you all for the informative replies. I'm learning something new each time I read the forum. However, if the repair is too costly, I might have to part this 1994 3800 and go for another one.

Are there any forum members in the Houston area?

Thanks all for the input. I've swapped out the PCM (or ECM) with a remanufactured one purchased from Advance AutoPart ($106 after tax) and car is working now. Towards the end, the car pretty much stalls immediately after engine is started, and sometimes it will run, but most time it won't. I did swapping back and forth between the old PCM and new PCM, and verified that it is the PCM causing the stalling. I also noticed a low frequency buzzing sound when the old PCM is attached, but I guess it will be almost impossible to find out what circuit is shorted (or broken) in PCM and fix it yourself.

I have a thread in the EVERYTHING ELECTRICAL AND ELECTRONICS on how to change the PCM (ECM) for your reference:
http://www.bonnevilleclub.com/forum/...ic.php?t=48162

Just a side note: about a year ago I had a chip controlling the A/C (can't remember the parts name) changed because it went bad. It was pretty expensive, something like $200 ACDelco parts and located approximately the same place as the ECM, could I have some sort of electrical problem in the vehicle? Shouldn't the fuse protect these equipment?