I have a 1987 240 sedan, which I use fairly heavily at work. (Construction inspection) I typically put ~500 miles on the car in a week, and up till now my baby hasn't given me any problems for about 7,000 miles.

On the way home today it was fairly warm (~92 degrees), the car hesistated several times (having replaced the AMM last February, I figured maybe a problem with the junkyard part). A mile later the car stalls completely. I tried restarting and the engine fired, intermitantly but wouldn't start. So, being almost home I walked with the intention of towing it myself to work on her tonight.

Three hours later when I came back she started up fine with none of the previous symtoms occurring. The car has been a little slow to start lately, (I think the fuel pump is going) but if the pump died, why would it run fine after a few hours? My thoughts so far are possible electrical probablems that are heat related. Any known problem areas on the 240 to check, or suggestions of where to go from here?

Based on your symptoms, my guess is that it's not the AMM. However, to test for that, the next time it does that, disconnect the AMM and see if it runs. The computer will assume the AMM is shot and place the car in "limp home" mode. It will run, but rough. As far as what else could be the problem, my best advice for a quick find is to go to the 700/900 FAQ, specifically here to check for ignition problems:

http://www.brickboard.com/FAQ/700-900/ElectricalIgnition.htm

I'm not sure, but I think I read somewhere that a faulty ignition coil when overheated may give the same symptoms. Maybe someone else can confirm/dispute this?
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1980 245 Canadian B21A with SU carb and M46 trans

Yeah, I had the same problem and the ignition coil was the cause. You should first check for good spark. If the spark is weak then you know that you need to replace either the coil, wires, distributer cap and rotor or something. But since it is heat related, the coil would be the most probable culprit.

When I had my problem, I looked at the spark, even when though it was cool out and the car wasn't exhibiting the problem. Comparing it to another 240, it seemed very weak. After swapping out the coil, the spark was huge! Like it should be. So, I replaced it and the problem went away.

If you check for spark and everything seems OK, then you might want to suspect the fuel pump relay. In hot situations the typical bad solder joints could cause a drop in voltage to the pumps and cause a similar problem.

When was the last tune up? Plugs, cap, rotor, wires, air and fuel filters? How old is the cat? Is the throttle body clean? Have you checked your fuses for corrosion, especially the fuel pump fuses? Does the '87 have the 25amp fuse on the fender under the hood?

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don hodgdon '89 744ti, '81 242t, '71 D-35...just waitin' for the glue to dry :-)