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Testing a MAP sensor

6737 Views 3 Replies 4 Participants Last post by  N0DIH
Does anyone know how to test a MAP sensor for a 1980 Eldorado? Its mounted near/on the ecm. My car runs rough when I come to a stop and it cutts out at takeoff sometimes. The timing is at eight degrees and it should be at ten, but the distributer is frozen in the block, i.e.- I can't turn it. My chiltons manual says that the map could be malfunctioning, but I hate to go and buy one and have it not repair the issue, like I have done so many times before. Is there a way to test them? Thanks.
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The map sensor can be disconnected from the circuit and checked with an ohmmeter andhand operated vacuum pump. Hook the pump to the vac port and look for varing resistance between 2 terminals with change in vacuum.
Which engine do you have?
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Ape Man,
That's a good test.

Here are a couple more, just for the heck of it.
If you have a scan tool.
  • Test the 5v ref circuit for 5volts
  • Test low ref circuit from the connector to ground for less than 5.0 Ohms with the key OFF.
  • Then connect the MAP sensor wire harness connector to the MAP Sensor.
  • Remove the MAP Sensor, and turn the Key ON .
  • Connect and operated the vacuum pump, look for a varing kpa or voltage value on the scan tool. This tells you the signal circuit, ECM/PCM and MAP Sensor are working OK.
One more, if you don't have a scan tool, but, you have a dmm.
  • Use the DMM on the voltage scale.
  • Jumper the 5v and low ref circuits from the MAP connector to the MAP Sensor.
  • Connect the DMM to the Signal terminal of the MAP and ground.
  • Connect the vac pump to the vac port and look for varing voltage at the signal circuit (approx 0.2 -4.90vots) with a change in vacuum.
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I did my Vortec 454 with my scan tool and a vacuum pump, read dead on. If same connector on newer cars/trucks and they have a good scan tool, connect it up to a friends car and be read that way.
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