Testing a MAP sensor

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5.0 and 5.7 Discussion, Testing a MAP sensor in Cadillac Engine Discussion; Does anyone know how to test a MAP sensor for a 1980 Eldorado? Its mounted near/on the ecm. My car ...
  1. #1
    Eldorado guy is offline Cadillac Owners Fanatic
    Automobile(s): '80 Eldorado, '50 Chrysler Windsor, '92 Ford F-250 7.3 4x4
    Join Date
    Jun 2006

    Testing a MAP sensor

    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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  3. #2
    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
    Automobile(s): '80 Fleetwood Coupe, 1994 and 1995 Mercedes 140 Coupe
    Join Date
    Feb 2005
    Southern NJ

    Re: Testing a MAP sensor

    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?

  4. #3
    FrankT's Avatar
    FrankT is offline Cadillac Owners Enthusiast
    Automobile(s): 99 STS
    Join Date
    Mar 2004

    Re: Testing a MAP sensor

    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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  6. #4
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
    Automobile(s): 94 Fleetwood Brougham
    Join Date
    Aug 2004
    Rockford, IL

    Re: Testing a MAP sensor

    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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