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Thread: Car won't start when it's hot outside?

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    Question Car won't start when it's hot outside?

    Hi guys. I have a 2002 Polo 1.4 and it always start but today first warm day hit Sweden (about 20+) and it will not start at all.

    Anyone know where I should start looking?

    It was the same last summer.

    To make it clear. It's always impossible to start when its hot outside and the car is "cold". Else it works like a charm. During winter if the car is warm it will start again. Really confusing?! =)

    Thanks in advance.

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    what are the symptoms?
    2000 Golf 3 1E, 1.8 8v - AAM

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    Administrator Crasher's Avatar
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    If a fault code read doesn’t show anything, I would suggest having a new crankshaft speed sensor fitted.
    "I disapprove of what you say, but I will defend to the death your right to say it"

    Evelyn Beatrice Hall (28 September 1868 13 April 1956)

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    Administrator Keithuk's Avatar
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    First posts normally go in introductions else you could get a free fix and we never see you again!!!

    Your car spec say 0, only what I've added from this thread.

    You need to get your motor scanned (preferably with VAG-COM\VCDS) for any error codes logged in the ecu and post them, that will save a lot of guessing and check systems out.
    2010 Golf GTD (170) CBBB, 5 Door, Shadow Blue (P6/D5Q), Transmission Code: KXZ, Flat Tyre Indicator, Basic Protection Pack + VCDS.


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    @SlippDiff Last summer when it stood outside in say 20 celcius it never started. The starter and battery work fine but it never fired up. Then when you wait until night it always started. The C meter in the car is always correct on the dash.

    @Chrasher I tried to read out the error codes but unfortunatley there are no error codes in the log? Is it common issue that the crankshaft speed sensor react to heat?

    @Keithhuk Ok, sorry about that. I can try to introduce me when I have a little more time. But I don't have anything to tell about my self, lol.

    Whatever. Today I was able to fire it up again but first time today it had more problems.
    It pendles idling between 900-1300 even when it went up warm to 90 degrees.
    But as soon I hit the gaspedal nothing happens at all, its still idling. The ECU lamp went on too.
    This was the first time it occured.
    Still it will not show any error codes in vcds...

    Any ideas ? Thanks again guys!
    2002 Polo 1.4, Petrol

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    Hi again. Now its getting even more strange. I went out now 00:40 and its approx 3 degrees outside. Now the gaspedal work and I can drive like normal?
    Also I tried a third OBD tool and this time I got 3 error codes out of it. Not even VCDS found them?

    P0170 (ECU 10) VAG: Fuel Trim Bank 1
    P2101 (ECU 10) OBDII: Throttle actuator control (TAC) motor - range/performance problem
    P0106 (ECU 10) VAG: Manifold Asolute Pressure (MAP) System Performance

    Does this tell you guys anything?
    Could it be the MAP sensor? Yet would the map sensor have issues getting the car to start when its hot outside?

    Thanks in advance again... Starting to think my car is haunted =D
    Last edited by PoloBeard; 25-04-20 at 00:47.
    2002 Polo 1.4, Petrol

  7. #7
    Administrator Crasher's Avatar
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    It says to be a dirty throttle body getting upset by a lot of messing around trying to solve a crank speed sensor problem.
    "I disapprove of what you say, but I will defend to the death your right to say it"

    Evelyn Beatrice Hall (28 September 1868 13 April 1956)

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    Thanks for the input Crasher. As I'm not familiar with fixing things like this... Should I just try to replace the crank speed sensor or clean the throttle body? Any help would be more than appreciated.

    Was also thinking of replacing the suction temprature meter but realized its also a temprature meter inside the MAP sensor? Are there 2 sensors in total ?

    Sorry if my English is a bit crazy as I'm in Sweden.
    Thanks again!
    2002 Polo 1.4, Petrol

  10. #9
    Administrator Crasher's Avatar
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    The MAP/IAT sensor is a combined unit in the side of the inlet manifold and is often replaced for this fault when it is not faulty. The first thing to do is remove the throttle body and throughly scrub it clean inside using carb clear and a stiff nylon brush, until it is spotless.



    Then you have to put the car on a battery charger so a minimum of 12 volts is maintained. Go into fault codes and erase them, the into Adaptation 10 enter 0, read and save and do this again twice. Then go into Basic settings 04 and enter 060 and wait whilst the throttle motor clicks and whirs, then wait another 15 seconds and turn off the ignition. Wait 1 minute and turn the ignition back on and wait until the throttle motors stops wiring and then start it.
    "I disapprove of what you say, but I will defend to the death your right to say it"

    Evelyn Beatrice Hall (28 September 1868 13 April 1956)

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    For what its worth... throttle faults and MAP faults and fuel trim will tend to go hand-in-hand with each other because the MAP sensor serves as feedback for the throttle actuator operation as well as being a key parameter for fuelling adjustment (trim) - the ECU will observe accelerator pedal position (APP), actuate the throttle and observe the MAP to see if the throttle actuation was correct (throttle opening results in increase depression in the inlet, measured by the MAP). Oxygen sensor readings provide feedback to the ECU about the fuelling after the combustion process. The ECU then learns the drivers driving style based on these things in order to adapt the injection & ignition map for optimum performance and economy.

    Try what Crasher suggests. I'd start there.

    (For me, whenever i hear of these kind of problems based (seemingly) purely on ambient temperature, i wonder if it's a faulty solder joint within an ECU (I've had these a few times and they always resulted in sending the ecu away for repair). But that'd need proper diagnosis. Can't diagnose this over the internet easily. You'll need an oscilloscope to see what's going on with the different sensors.)
    2000 Golf 3 1E, 1.8 8v - AAM

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