The one behind the plenium had a wet oily film in it when you pull the hose. My guess is that there is a rubber diaphragm in there and the oil might cause problems and a false reading.
Dave
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Last edited by mgbrv8; 03-06-2013 at 06:00 AM.
I had a map sensor fail. It caused the car to cut out and die several times until the ECM took over and set a value based on the TPS. I cut the map open to see what gives and found a 10 ohm resistor came off the solder pads. The vaccumn port sensor on the circuit board appears to be a solid state device and is sealed except for a very tiny hole in the middle of a metal disk. Under the disk is a tiny solid state device with several leads and this device has a clear spongy film covering the surface that the metal disk acts upon. The entire circuit board (not the solid state device)was covered with a gelatin Like substance which i believe prevented dirt and moisture contamination. My MAP sensor had a 3/4 volt lower output than the new one i installed before it went intermittent. The entire circuit board measures about 1 inch wide by 2inches long. The rest is all plastic filler material.