Still havent diagnosed my 1987 240 yet. In brief:
It has a rough idle, stumbles on acceleration, little power, does fine above 40 mph but sometimes stalls when coming to a stop. The tach will also drop to zero for about 30 seconds.
Cannot find vacuum leak. Actaully I found one in the flame trap vacuum but clearing it and replacing the flame trap didnt help. Fuel filter was replaced, air filter replaced, plugs are okay.Fuel pressure regulator seems fine. It idles higher when vacuum tube is taken off and the fuel test shows its pumping through at a reasonable rate on idle.
One brickboard poster suggested the Air Mass Meter. I did the test between the 2nd and 3rd relay. The range is 3.5 to 4.0 ohms. Mine was registering 3.2 Is this far enough out of range to warrant replacing? The other test said the relays should read 108. I got 20.8 ohms but think I tested wrong.
I'm reluctant to replace the AMM without a confident diagnosis.
ALso when I unplug the AMM the idle is the same but when I step on the gas it stalls. So I don't think its completely dead.
Can anyone second the diagnosis of the AMM?
Thanks.
I think I'm getting close here.

When you cleaned the TB did you get all the holes and passages cleaned also? Did you remove and clean the black plastic base idle adjust knob and its seat?, it gets very dirty in there.
If you remove the AMM connector (engine off) does the ide improve, if so AMM may be bad. Dan

I should also mentioin that these conditions started suddenly. Everything was fine and then one night it started stalling and bucking.

When did you last clean your throttle body? And your idle control motor?
I assume you have already checked your air intake hose (between AMM and TB) and that it does not have any air leaks.
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'89 244DL M47 162K miles

I checked the air intake hose and it was fine. I havent cleaned the throttle body or the idle control motor. I've stayed away from the throttle body because it didnt seem like the throttle would make the rpms bounce around. I've stayed away from the idle control because it didnt seem like the idle control would effect acceleration. Maybe I'll check those next. Are they fairly simple processes?

Do the iddle control motor next, even if it won't affect acceleration, it may help improve your iddling, be carfeul not to spray the switch with carb cleaner though. Yes the idle control is very easy to do, just unplug it and remove it from the car, you can use carb cleaner and Q tips to clean it, you should see some blow by and grimy stuff come out as well. While you have the IAC out checked the hoses that connect to it to make sure they have no cracks, especially the one that in shoulder shape and goes under the TB.

Also on the board do a search on the Zero Mile list, you'll get a good list of things to look at .
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'89 244DL M47 162K miles

Yes and you should definitely clean them both. You will need a new gasket for the TB which you can get cheap at FCP Groton. For instructions check out the FAQ here on the board, or I recall a very good post on TB cleaning from CarmaticLove, i.e. Jon Batista. Also if you go on the IPD Web site (IPDUSA.com) you will see next to the carburator TB cleaning kit they sell a Pdf file which you can download for free, it contains pictures and detailed instructions, don't bother buying their kit, you can simply get some TB cleaner at your local store for a couple dollars and use an old tooth brush and some rags.

I had some stalling issues (warm engine) and a rough iddle, it all cleared up and went back to normal after cleaning my TB and the IAC.

Anyway these are simple enough regular maintenance items, and very cheap to do.
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'89 244DL M47 162K miles

I just cleaned the throttle body and that didnt do the trick. I think there was some improvement, it definitely needed cleaning anyway. Thanks for the suggestions. Even if I'm not solving the problem the car is getting a round-a-bout tune-up.