Does anyone know on a '93 960 (B6304F with Motronic 1.8) which wire on the MAF sensor is the signal return and which wires control the burn off signal? The wires at the connector pins are colored: #1 BN (ground), #2 BN/W (goes to ECM pin #26), #3 GN/Y (goes to ECM pin #7) #4 Y (goes to pin #25) and #5 GN/R (signal input voltage). With the ignition in the ON position and the engine OFF, the voltages are #1=0 volts, #2=0 volts, #3=1.4 volts, #4=0 volts, #5=12.6 volts. If pin #3 is the signal return, then the voltage across #1 and #3 should be 0.1 to 0.2 volts which implicates a faulty MAF. And that would explain why the car runs rich all the time, gives error code 512 and does not run any better or worse with the MAF sensor plugged in or unplugged. I cannot tell which two pins would show the 1 second burn off when the engine shut off. I could not detect the burn off signal but the car is not warmed up and has only been idled a few seconds each attempt to detect it, if that matters. Any help is greatly appreciated. Thanks.

 

I don't have any wiring diagrams so I can't help you on that aspect.
Check really good for a big vaccum leak.
Short term fuel trim usually means a Big vacccum leak.

 

I haven't found a vacuum leak yet, but it idles a little higher and smoother if I disconnect the vacuum line heading over to the check valves for the climate control. The vacuum there was a strong 14lbs or so. Thanks for the tip.

 

Also do your brakes feel funny at all?
If so check the booster as well.

 

For the benefit of others researching similar problems, the AMM (aka MAF) was replaced with a rebuilt unit. Performance did improve but not fully. Vacuum leak finally traced to a vacuum modulator on the climate control system. Once that leak was corrected, the engine ran much better.