Subaru Impreza, hard to start, check engine light on

Discussion in 'Subaru Impreza' started by mountaindog, Mar 25, 2005.

  1. mountaindog

    mountaindog Guest

    I have a 95 Subaru Impreza.

    In the last 6 weeks the check engine light goes on and off. At cold
    startup it is always on. In the last week it has been on permanently.
    With the key in the on position the system runs the fan at all times
    cold or hot and it continues to run when the engine starts even when it
    is cold, like 30 degrees and stays on when the temp is up to normal.
    When connecting the diag system under the dash to get the the check
    engine flash codes it seems to be pointing at almost every sensor in the

    11 crank
    13 cam
    21 temp
    23 O2
    33 speed

    After the engine is up to operating temp it runs fine but, the check
    engine light stays on and so does the fan.

    It takes 10 to 20 attempts to get it started. Each time it will turn
    over a few more times until if fumbles around enough to keep running,
    then it smooths out and runs fine. No power loss, it seems to run fine
    and then will restart fine. It seems as though the system can't tell
    the engine temp so it does not know how to manage the fuel at cold
    startup. As the engine warms up the temp gage seems to show valid readings.


    Is the temp sending unit used for the dash gage and the EMU?

    Where is the temp sensor on this engine and is there
    more then one? I know where the other sensors are buy I don't
    know where the temp sensor is.

    Is there any particular sensor to replace to just do a test. I have two
    of these cars so I can swap parts looking for the problem. As usual the
    dealer will not tell me anything.
    mountaindog, Mar 25, 2005
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  2. mountaindog

    Remco Guest

    I had the same problem on my daughter's Subaru last year. Look if you
    can start the car with the ECM reset connector on -- look on the web,
    as there are several sites that will show you how to do this.

    If it then starts, it is most likely the thermosensor. It is sitting
    near where the coolant comes in op top of the engine. Let me know if
    you need help locating it.

    Hope this helps,
    Remco, Mar 25, 2005
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  3. mountaindog

    Bob Bailin Guest

    A bad crank or cam sensor would cause hard starting,
    and a bad temp sensor that's always indicating hot would
    result in the fan running all the time.

    The one thing they have in common is an engine ground.
    Check the ground wires to the engine to make sure they're
    not rusted out at the connectors. And check the battery
    cable connections for corrosion build-up which you can
    scrape away with a flat-blade screwdriver. This will
    clear the codes from the ECU, so that you can see which
    trouble codes come up first next time you start the car.
    And make sure the battery isn't undercharged (13 volts
    when the car is off).

    Bob Bailin, Mar 25, 2005
  4. mountaindog

    Remco Guest

    That's a good point, Bob.
    I forgot to mention that the fans are running even with the engine
    cold, if the thermosensor is bad. That is a surefire way to tell if the
    sensor is bad.
    Remco, Mar 25, 2005
  5. mountaindog

    mountaindog Guest

    I connected the EMU reset and diag connecters together (under the dash),
    one brown set and one green set. Yesterday the car started right up and
    it was cold outside, 19 degrees yesterday here in Utah at 8000 feet.
    The next day I unplugged the connectors and the problem is back.

    My wife and I each drive Imprezas hers, the one with problem is a 95 and
    my car is a 94. For a test I unpluged what seems to be the Temp sending
    unit on top of the engine, near the alternatory on the 94. I was
    expecting a check engine light but this did not happen and the car
    started just fine and the fan did not run. After doing this the temp
    gage is no longer working. So I am still wondering if there are 2 temp
    sensors on the car. One for the gage and one for EMU. Why would I not
    get a check engine light when I unplug this sensor?
    mountaindog, Mar 26, 2005
  6. mountaindog

    Remco Guest

    Right - there is one temp sensor for the dash, one for the computer.
    Are both your fans on when it is failing?

    I am pretty sure I made pictures of the repair - let me know if you
    want me to dig them up. It is in a little bit of a weird spot; not hard
    to get to, but hard to find.

    Remco, Mar 27, 2005
  7. mountaindog

    Remco Guest

    I dug out a couple of pictures of where the thermosensor is located on
    a 95 Impreza:

    You won't have to drain a lot of coolant, but do drain some of it
    because it will make a mess if you don't. The draincock is on the
    bottom of the radiator, along the back, towords the passenger side. It
    looks like it has plastic "mickey ears". Be careful turning it because
    they tend to snap, being plastic (don't ask me how I know :)

    On picture 1 drop down along one of the rubber tubes next to the arrow.
    You'll see that tube in picture 2 and the socket to the sensor as well
    (it was brown on mine). You'll need a deep metric socket (I forgot the
    size) on an extender because you can't access the thing with a socket.
    You can work it in using the approximate angle of the arrow in picture
    1. You won't have to remove anything (besides of course the
    thermosensor) but the extender will just clear what is around it.

    Don't be tempted to use teflon on the threads -- it doesn't need it
    and, from what the dealer told me, will actually screw things up. Also
    be sure to include the brass washer under the sensor.

    After you've done the repair, reset the computer with that green/black
    connector -- just replacing the sensor is not enough as the ECM will
    still think it has overheated.

    Hope that helps. Let me know how you make out.

    Remco, Mar 27, 2005
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