Location of TCC plug

I am having the stalling problem after my 3.1L 1993 Lumina sedan warms up. Driving on the highway car will simply stall, pull over, wait a minute and starts right up. Car has been well maintained and only has 52,000 miles on it. Car also shakes between 50 and 60MPH and then levels off at 65MPH. I do not have the shaking problem when I set the gear shift at D instead of the overdrive D. I've read about pulling the TCC plug and where it is located but I'm not sure I have found the correct plug. The plug I found is on the driver's side of the trans under the air filter assembly facing the front of the car. I've seen it described as a square plug with 2 or 4 wires and usually blue. The plug I'm looking at is round with at least 6 wires coming out of it. Is this the right plug?

I don't think so...they are square, four wire like this

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in the area you describe, forward driver's side, down low.

That will stop the shudder, but the stalling when moving is not a TCC trait, unless you mean when coming off the highway to a stop it stalls...that's typical.

I think there's a dedicated fuse for it on your year too, you can disable it that way too....

Only plug I find is the one I described. There is a fuse for the TCC but the main cooling fan is on the fuse also. I've been driving the car with the gear shift on D instead of overdrive D for 2 days and it has not stalled and no shudder. The stalling I was getting on the highway before when I drove it with overdrive D occurred randomly if I was slowing(not braking) from 65/70mph due to traffic conditions. Sometimes the car would stall stopped at a light but only after driving for 15-20 minutes. Also, is it alright to drive at 65-70 mph on D instead of overdrive?

You found the correct plug. However, your car has the electronic trans, and you cannot just unplug it, as that plug also controls shifting through the ECM. If you unplug it, your car won't shift. Your problem sounds more like an ignition issue (coil, ICM, worn plugs/wires) or a bad ECM. The speed at which your problem occurs is right at the converter lock-up threshold, and the engine is lugging, so a misfire caused by the parts mentioned above will cause exactly what you describe. If your tune-up is overdue, try new plugs, wires, fuel and PCV first. If it doesn't clear up, then you may need an ICM or coil(s).

Thanks, I'll have it checked. What about driving on D instead of overdrive? What max speed is safe?

Just tried to start the car so I could take it to get checked out and it won't start. Starts up, chugs and dies. Did this 2 or 3 times, now won't even do that. What a nightmare.

Couldn't even jump start the car. Bought a new battery and was able to start almost immediately. I drove the car around for about 15 minutes with no stalling. Went on freeway, stalled as soon as hit 60mph. Waited a minute, started again and took off down the freeway. This time I made it about 500 feet before it stalled again. Got off freeway after restarting and drove around for almost an hour on side roads without stalling, even at stop lights. Now I'm really confused.

There seems to be elements of two possibilities: one is easy to clear up. ON one side TCC shudder is very likely and this can be solved easily: pull the TCC plug out and remove conductor D (tan with black stripe) from the plug
http://www.avigex.ca/xport/tccconnector.jpg
then reinstall the plug so all gears shift normally, except TCC will not apply. (some have installed a switch on that wire so they can enable or disable TCC at will). YOu will have the Check engine light ON however. THis will provide answers to the "misfires" around 55-60 which is speed at which TCC applies. YOu will see what happens and report. IF it clears, you have your answer, if not you know you have to look elsewhere..but at least it will have cost 0$ fot this test.
Another possibility for stall is stuck TCC due to fault of the TCC solenoid..it has been reported several times on these forums and this stalls the engine when trying to stop as TCC stays ON...if that was cause here, it could also be cleared by disconnecting PIN D as TCC would not apply...unless the valve itself is damaged and leaks even if not electrically energized.
After that test, you will be left with the other options if problems continue. ANyway, you mentioned engine "stalls" at highway speed....if that means it "stops" then obviously there is some other problem, either alone or in addition.

Had fuel filter changed this morning and car would not start. Tried for 5 minutes without luck. Started once or twice and died immediately like it was starved for fuel. Stopped trying once there was heavy gas odor. Will try again once car is cold. I'm thinking it's the fuel pump.

Well if if smells fuel, check for spark: unplug one spark plug wire, install a spare spark plug , let it rest on engine block and start while some one checks for spark. THis is easy and result will direct for the proper options....

No spark. Having it towed to shop.

Position sensor and ignition module are common failure scenarios, in fact, at that age, should be considered preventive maintenance items.

The way it's randomly dying, I'd have the ECM checked for water intrusion. The OEM service number 1227727 is a known troublesome unit, and will cause random no starts, no spark, no fuel, etc... I also agree with LMP to have the igniton module and coils checked, as well as the wiring from the crank position sensor to the ICM, as it runs close to both the passenger side axle shaft and the harmonic balancer.

It's the ECM, water inside. Now they have to find one.

Shop put in a another ECM today. Was able to read ECM this time but car races at idle, used up 4 gallons of gas in about 20 minutes. Rest of readings all out of whack. Have to get another one. If next one is bad, I think I'll have a bonfire.