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Thread: M50 sensor terminology clarification

  1. #1
    Join Date
    Feb 2005
    Location
    Houston, TX, USA
    Posts
    137

    Default M50 sensor terminology clarification

    Could someone please tell me if any of the following terms are redundant?

    Reference Sensor
    Camshaft Position Sensor
    Crankshaft Position Sensor
    Pulse Generator

    Which one(s) are in my M50 engine?
    Which one(s) could be telling the DME to idle improperly?

    Thanks.
    Ryan
    1994 525iT

  2. #2
    Join Date
    Oct 2004
    Posts
    3,395

    Default

    Both the first and the last are generic terms for many different inputs used throughout the car. A pulse generator can be an ABS coding ring sensor, a diff speed sensor, and any number of other things I can't think of right now off the top of my head. Same applies for "reference sensor".

    The M50TU has a number of items that should be checked if idle isn't normal. What, exactly, are the symptoms?

    best, whit

  3. #3
    Join Date
    Dec 2003
    Location
    baton rouge, loserana
    Posts
    6,922

    Default

    the first thing to look for with idling problems is air leaks, on the m50 motors one of the most common leak points is the two lines comming off the valve cover rot off, the big one goes to the air boot sometimes going through a small tube atached to one of the supports for the manifold before it hooks to the boot, the small ones goes to the fitting that the idle control valve ataches to under the intake about dead center with the nipple facing the front of the car
    all america wants is cold beer warm cat and a place to take a poop with a door on it

  4. #4
    Join Date
    Feb 2005
    Location
    Houston, TX, USA
    Posts
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    Default

    Thanks for the information on idle problems, but I should have qualified my question. I have actually searched through the forum and I did not immediately jump to this as the culprit.

    Here is the litany of things I have tried:

    New fuel pump and sender
    New fuel filter
    New fuel pressure regulator
    New fuel injectors
    New idle control valve
    New intake temp sensor (the one in the bottom of the manifold)
    New spark plugs and connectors and tested coils
    Tried a different air mass meter
    New oxygen sensor
    Propane test for vacuum leaks
    Carbon buildup removal (in the shop)
    Truckload of fuel system cleaners
    Tested throttle position switch: resistance varies from 0.80 Ohms to 4.75 Ohms without interruption.
    New intake manifold gaskets.

    Really my question was just about the sensors. I am going to buy a crankshaft position sensor or a camshaft position sensor or both if my engine has both. I just wanted to start with the most likely suspect.
    Ryan
    1994 525iT

  5. #5
    Join Date
    Feb 2005
    Location
    Houston, TX, USA
    Posts
    137

    Default

    It is kind of a growl at idle and hesitates when accelerating to highway speed. Once it is there, it is smooth. It feels like a timing problem.
    Ryan
    1994 525iT

  6. #6
    Join Date
    Mar 2004
    Posts
    404

    Default

    Remove and inspect the intake boot for cracks.

    Paul Shovestul
    .....Got to keep the loonies on the paath.

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