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Thread: Coolant temperature sensor

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    Me? Post? Never! Club Member Konrad's Avatar
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    Coolant temperature sensor

    ...this time trying to locate one on NA engine. It's NOT on the front of the engine, I suspect one on the right side of engine, just under inlet manifold, but i'm just not sure how many wires should go into it - 1 or 2. Is it quite big sensor with 2 wires sitting just under first front inlet manifold pipe?
    Jola's NA is running quite rich and doing around 15mpg. I did exchange O2 sensors from known, well running engine and fuel consumption did not change, so I suspect coolant temp sensor now. Are there any other hints, why she would start drinking fuel like TT? Engine is going smooth, just very thirsty.
    Who am I? By Tima - Metropolis.

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    I'm part of the furniture Moderator Ian C's Avatar
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    Right hand side front. Follow the top rad pipe to the engine and you'll see two sensors. One should have one wire, thats the one for your temp gauge. The two wire one is the one that the ECU actually uses.
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    Me? Post? Never! Club Member Konrad's Avatar
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    Thank you good Sir
    Who am I? By Tima - Metropolis.

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    Me? Post? Never! Club Member Konrad's Avatar
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    Ok, both O2 sensor replaced for known good ones, temp sensor also replaced for a good working one, car still doing 15mpg. What's next? It does go smooth, free revs are as usual...
    Who am I? By Tima - Metropolis.

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    What search button? MEMBERSHIP EXPIRED
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    maybe try an ecu reset

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    ps3 tag wiggyno1 Events Organiser TT Paul's Avatar
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    what about the fuel pump or fuel pump ecu maybe
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    Age. Fac ut gaudeam Club Member Tricky-Ricky's Avatar
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    Have you checked the fuel pressure regulator?
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    Me? Post? Never! Club Member Konrad's Avatar
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    Looks like O2 sensors and coolant temp sensor are not the cause, got swapped with known working ones and she is still burning tons of fuel. ECU was reset too.
    @Tricky
    Does it have any influence on fuel usage? Car is running perfectly fine if you ask me, no missfires, no lags, it's just using a lot of fuel...
    Who am I? By Tima - Metropolis.

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    Me? Post? Never! Club Member Konrad's Avatar
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    Quote Originally Posted by Tricky-Ricky View Post
    Have you checked the fuel pressure regulator?
    How can you check it? Workshop manual is showing only how to remove and install it again. Should I fetch one from other car and test it?
    Who am I? By Tima - Metropolis.

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    Age. Fac ut gaudeam Club Member Tricky-Ricky's Avatar
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    Quote Originally Posted by Konrad View Post
    How can you check it? Workshop manual is showing only how to remove and install it again. Should I fetch one from other car and test it?
    There should be a resistance value in the manual, don't forget that there are two, one for the display and one for ECU.
    I'll take a look later, and yes it has an influence on the fuelling, in that the ECU thinks the car is cold all the time and so will run rich all the time.
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    I'm part of the furniture Moderator Ian C's Avatar
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    Check the Ox pin on the diagnostic port with a multimeter when the car is warm idling, that will give you an indication of if it's fuelling correctly in closed loop or not.

    It should bounce around between 0 and 1 volt, if it's sat at either 0 or 1 volt constantly, the fuelling is wrong
    I love my job. It pays for my Supra.

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    Me? Post? Never! Club Member Konrad's Avatar
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    Will try it first thing in the morning, thanks guys

    @Tricky
    Could you just tell me what values should FPR showing and where to measure resistance?

    @Ian
    Ox pin will show O2 measurements if i'm not mistaken? Will check this one too, but I think o2 sensors and coolant temp sensor are fine. Trying to have a look at FPR.
    Last edited by Konrad; 16-05-10 at 00:40.
    Who am I? By Tima - Metropolis.

  13. #13
    I'm part of the furniture Moderator Ian C's Avatar
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    Quote Originally Posted by Konrad View Post
    @Ian
    Ox pin will show O2 measurements if i'm not mistaken? Will check this one too, but I think o2 sensors and coolant temp sensor are fine. Trying to have a look at FPR.
    Yes, it gives the O2 sensor measurements. Regardless of the sensor being fine or not, it'll tell you something useful. If it's bouncing around stoich then your car is fuelling just fine, so your excessive fuel usage must be caused by open loop operation. If it isn't, then either the O2 seonsr is reading wrong or the ECU is getting a confused signal from something. It's an easy diagnostic step
    I love my job. It pays for my Supra.

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    Age. Fac ut gaudeam Club Member Tricky-Ricky's Avatar
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    Quote Originally Posted by Konrad View Post
    Will try it first thing in the morning, thanks guys

    @Tricky
    Could you just tell me what values should FPR showing and where to measure resistance?

    @Ian
    Ox pin will show O2 measurements if i'm not mistaken? Will check this one too, but I think o2 sensors and coolant temp sensor are fine. Trying to have a look at FPR.
    If you have the manual its page EG652, the sensor is supplied with 5V from the ECU and detects the temp via voltage change, there is a table of acceptable readings, but an interesting point is that if the sensor fails there will be an error code 22, but in that case the ECU assumes a default temp of 80C and so shouldn't make any big impact on fuelling.

    But i guess if its just not giving the correct temp feedback it will change fuelling, had similar on several Nissan's.

    IAT fault will also change fuel trim but not in a big way, just a thought are you doing more short journeys? makes a big difference to fuel consumption.

    Other than that if the O2 sensor output is showing stoic then maybe like Ian says there must be some other problem perhaps with ECU sensing open loop all the time, do you know anyone with a wideband you can test on the move with?
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    Me? Post? Never! Club Member Konrad's Avatar
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    Ok, tested O2 sensor outputs and both are bouncing between 0.12 to 0.84V. Changed FPR from other engine and will see if it will give any effect
    Who am I? By Tima - Metropolis.

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