Our '93 240 lately, and inconsistently, has been showing a rough idle and surging acceleration. It has been coupled with a periodic battery failure. (This has been solved; a broken ground wire on alternator.) Here's what I know:

main fuel pump seems/sounds OK
in-tank fuel pump sounds OK, and problem is present regardless of fuel level
fuel filter has 32K on it
measured fuel pressure is 35psi
ignition module is good
AMM is good
throttle body is/has been cleaned
O2 sensor is good
fuel pump relay tests good (clicks at key turn)
new plugs/wires/cap/rotor

As I said, the problem is inconsistent, in both its frequency, and in its magnitude. For most of the past several weeks the care surges when under load, slight or great. Sometimes this is coupled with a rough idle, other times not. Sometimes the car seems to run just fine, with no idle or acceleration issues. When it is present, it can very from a slight stutter or delay when accelerating, to a pronounced loss of power such that the car lurches.

Thanks to any and all who might offer insights on what to check next. My local, while not a foreign or Volvo specialist, has a logical mind and keys in correctly I think. He too is stumped.

Remove and clean the idle air control unit and check for vacuum leaks in air intake hoses.

from FAQS:

http://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm#Cold_Start_Dies_Dirty_IAC

There is a connector under the dash on the passenger side that connects wires between engine compartment and interior. If disconnected it will shut down a lot of electronic readings (AMM, etc...) I've had that connector come loose on my 91 245 and cause sporadic problems, even a no start.

So look for a white plastic connector with multi-color wires up high on the passenger side of the center console. Make sure it is securely fastened.

Good luck.

Bert