1988 240DL will go into a retarded timing type of power loss. It will do this whether the gas tank is full or empty. Mostly when the humidity is high, although not always. I think I can hear an electrical relay type of click when it derates, and again when it returns to normal. One fitful time the car would accelerate from stopped to 10 MPH normally, then just switch to no power. Pressing the gas pedal did nothing for increased speed, just got the low "waaah" sound like a carburated car starving for fuel. It did this repeatedly, 5-6 trials, then when I shut the engine off and restarted right away the car ran okay again. I've changed all the fuses, O2 sensor, fuel relay, under body fuel pump, distributor cap, rotor and set timing. Once the car is up to steady speed it runs reasonably well, but will not accelerate like it used to and takes a very long time to wind up RPM's. Air Mass Meter is original as is wiring and Catalytic Converter. Air filter has been changed recently. I'm ready to take it to a repair shop but like to be armed with some information from people who may know what this condition stems from.