Here is a fun one that's not been so fun now and again for me.

Have an 88' 240 wagon 150k. Ever since owning the car, two years, I've had intermitent power loss. At first it was real bad, it wouldn't go hardly at all much of the time. Often the problem would be solved by simply restarting. Since those early bad times, a few things were replaced and the problem is relatively rare and the power loss is only severe when stomping the gas and when you want to go over 60 or so, pass etc. The transfer pump, main pump, pump relay, ECU, Line Pressure regulator are all newish and the problem still occurs. Seems to leave the Air Mass Meter. Did try two or three used ones and some made it much worse from the git go but can't remember if any were just the same, none solved it. There may be an adjustment nessesary to get the mass meter to work right. Remember, the problem is usually instantly solved by turning the engine off (often without stopping) for the shortest period. Sometimes it will come back fairly soon on a long trip, sometimes not, but it will nearly always be solved that way.

Happy Troubleshooting.