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Corsa C low idling

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  • [Corsa C] Corsa C low idling

    Hello all,

    I posted a month or two ago on piston heads about a low idling issue with my partners Corsa C 1.2 Twinport. I explained that we had changed the throttle body, cleaned the mass airflow sensor however this had no affect. I was advised by others on the forum to get a scanning tool that can pull information about the cars performance, which is what we did. As can be seen with the data below there was a few things that stood out to me mainly the desired Idle speed, I did reset this however it just stayed the same. I have never really analysed car data before and I was wondering if anyone can see anything below that stands out as majorly incorrect that could be causing this low idle.

    Thank you all for your help.

    James.


    Measuring blocks information:

    Battery Voltage 14.3 V
    Main Relay Active
    Fuel Pump Relay Active
    APP Sensor 1 (Accelerator Pedal Position) 0.97 V
    APP Sensor 2 (Accelerator Pedal Position) 0.49 V
    Calculated Pedal Position 0%
    APP at Idle Position (Accelerator Pedal Position) Active
    TP Sensor 1 (Throttle Position) 0.80 V
    TP Sensor 2 (Throttle Position) 4.31 V
    Calculated Throttle Position 3%
    Throttle Position Idle
    Engine Speed 714 RPM
    Desired Idle Speed 730 RPM
    Mass Air Flow Sensor 1.39 V
    Mass Air Flow Sensor 7 kg/h
    Coolant Temperature 1.38 V
    Coolant Temperature 75 °C
    Intake Air Temperature 3.12 V
    Intake Air Temperature 30 °C
    Port Deactivation Position Sensor 2.8 V
    A/C Information Switch (Air Conditioning) Not Programmed
    A/C Pressure (Air Conditioning) 0.00 V
    A/C Pressure (Air Conditioning) 0 kPa
    Tank Sensor 1.94 V
    Tank Sensor 24 L
    Brake Switch 1 Inactive
    Brake Switch 2 Inactive
    Clutch Switch Not Programmed
    Vehicle Speed 0 km/h
    EGR Valve (Exhaust-Gas Recirculation) Inactive
    EGR Position Feedback (Exhaust Gas Recirculation) 0.76 V
    Fuel Tank Ventilation Valve Active
    Knock Control Inactive
    B1S1 O2 Sensor Heater (Bank 1 Sensor 1) Inactive
    B1S1 O2 Sensor (Bank 1 Sensor 1) 156 mV
    B1S1 Air/Fuel Ratio (Bank 1 Sensor 1) Lean
    B1S2 O2 Sensor Heater (Bank 1 Sensor 2) Inactive
    B1S2 O2 Sensor (Bank 1 Sensor 2) 451 mV
    B1S2 Air/Fuel Ratio (Bank 1 Sensor 2) Rich
    B1 Long Term Fuel Trim (Bank 1) -2%
    B1 Short Term Fuel Trim (Bank 1) -2%
    O2 Sensor Loop Closed
    A/C Relay (Air Conditioning) Not Programmed
    A/C Cutoff Mode (Air Conditioning) Underpressure
    Cruise Control Not Programmed
    Cruise Control Tip Switch Not Programmed
    Vehicle Speed in Cruise Control Range Not Programmed
    Malfunction Indicator (MI) Off
    Service Vehicle Soon (SVS) Indicator Off
    Oil Pressure Underpressure
    Remaining Oil Life 87%
    Engine Oil Change Warning Inactive
    Ignition Status On 12V
    Throttle Position PWM Servo Signal 14%
    TP Sensor 1 Learned Lower Position (Throttle Position) 0.70 V
    Engine Speed 1429 RPM
    Injector Time 3.3 ms
    Ignition Dwell Angle 1.6 ms
    Ignition Spark Angle 10.7 °CA
    B1 Knock Sensor Signal (Bank 1) 0.6 mV
    Knock Retard Cylinder 1 0 °CA
    Knock Retard Cylinder 2 0 °CA
    Knock Retard Cylinder 3 0 °CA
    Knock Retard Cylinder 4 0 °CA
    Normal Engine Operating Temperature Inactive
    Fan Control 1 Inactive
    Fan Control 2 Inactive
    Fan Control 3 Inactive
    Deceleration Fuel Cutoff Inactive
    Vehicle Acceleration 0 m/s2
    Full Load Enrichment Inactive
    Catalyst Protection Enrichment (Bank 1) Inactive
    ETC Limp Home Mode (Electronic Throttle Control) Inactive
    Electronic Throttle Control Learn Counter 11
    Vehicle Speed Pulse Not Received
    Immobiliser Function Programmed Yes
    Security Wait Time Inactive
    BCM: Vehicle-ID is programmed (Body Control Module) Yes
    Instrument: Vehicle-ID is programmed Yes
    BCM: Status of Vehicle-ID (Body Control Module) Okay
    Instrument: Status of Vehicle-ID Okay

  • #2
    Hi Welcome to the forum

    I have waited a bit to see if anyone else more knowledge gives you the definitive answer you are hoping for. I am no expert. These mystify me too. Amazing what the little blighters monitor.

    But a few things intrigue me. What is the idling speed you are getting on the dashboard rev counter? If its about the 714 rpm shown on the readout that doesnt seem very far short of the 'desired' idle speed of 730 rpm . 730 may be the desired standard for this engine so possibly that value cannot be changed. Is that what you tried to do? Do you know what the 1429 RPM shown further down is about?

    If you are idling at 714 rpm are there particular symptoms that makes this unacceptably slow. If its running rough you could try a new set of spark plugs unless they have been recently changed and even if they have check that the electrical connections where the coil pack connects onto the spark plug are clean and free of white or green corrosion. Also putting a bottle of fuel injector cleaner in the tank might help. If such measure improve smooth running the ide speed might also rise slightly as a consequence.

    The coolant temperature is shown as 75C. This is not yet fully warmed up. i would expect more like in the 90's. If it was definitely fully hot when you took the readings maybe the coolant sensor is reading too low, which might affect how the ECU adjusts things. Same with intake air temperature being 30C. Does this seem about right to you for the ambient weather, but allowing for heat within the engine compartment?

    The bank 1 air/fuel ratio being lean on sensor 1 and rich on sensor 2 may well be relevant . But I dont know if this is normal,or if not,how to fix it. Others may be able to help further.

    Sorry, its more questions than answers. Can you let us know how you get on. It may help others.

    Comment


    • #3
      Hi Welcome to the forum. I can see from your data the car is idling at 714 , when it should be 730. I know it would be slightly annoying for you.
      But from your data sheet everything seems to be ok . O2 sensors, short fuel trims all look ok . It could be a slight air leak somewhere or a poor connection , on a 15 year old car . Those readings on the data sheet look pretty good to me .

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      • #4
        You wait all night for a bus and two come along at once.

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        • #5

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          • #6
            Hahaha very true and thank you all for your responses!

            Over the last few months we have tried: changing the air filter, cleaning the MAF sensor (which increased idle revs by 50), checking for a vacuum leak and fitting a second hand throttle body and throttle position sensor all with no success. The only indication of what could be causing this was when we un-clipped the throttle position sensor pigtail which increased the idle to 950rpm, which is what gave us the idea of changing out the throttle body and throttle position sensor but this didn't fixed the idle issue. As when we unclipped the pigtail the idle returned to normal so could this be an ECU issue? I note from the data that the target idle speed is 730rpm that seems kinda low to me with other cars I have driven over the years. On the dash it shows the revs to b 550rpm under idle which is different also.


            I appreciate the responses as me and my partner are completely stumped so, we want to fix it were just not sure what is wrong hahahaha.

            James.

            Comment


            • #7
              As I said before, all the live data looks spot on . Most 1.2 corsa idle about 750 rpm . A lot of the engine sensors reading off the ECU are 5 volts.
              and a slight bad contact on the ECU or one of the sensors could be why it's idling just under the 750 rpm.

              Comment


              • #8
                Vauxhall specs for Z12XEP engine (if I remember correctly is the twinport) are 670-830rpm dependent on a lot of factors ie air density, fuel quality, temperatures etc.

                Which diagnostic tool did you use?

                Ecu requested values are always slightly different to the actual value, the fact you are seeing a totally diffrent rpm on the dash compared to what the diag tool/ecu are reporting would have me suspect a problem at the dash, a poor connection at the rear of the dash (a known problem on the corsa c) or possibly a dodgy rpm guage. A quick easy free test - you could try pushing on the dash or get your hand up behind the dash and give the wiring' the wiggle test'. It's not a definitive test but if this does make a change you'll know the problem area.

                Is the car running ok?

                Also in you diag report i noticed another engine rpm speed of 1429, did you give it some gas at some point??

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                • #9
                  hi guys I have the same problem with my wifes 2001 1.0 litre, I've changed the mas .the 02 sensor and the egr valve, but it's still runs sluggish, even stalls. someone said blank the egr valve, can anybody help .

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                  • #10
                    A quick check that you could do is unplug the MAF and 02 sensors at different times and take the car for a drive and see if there is any different in the running of the car . Obviously this will bring on the EML . If you haven't got a scanner to turn the light off . Just disconnect the battery will reset the EML .

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                    • #11
                      I have disconnect the 02 sensor but the car didn't start .

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                      • #12
                        Do you know there are two 02 sensors ? Have you tried just disconnecting the post cat one down at the back of the engine . Have you got any engine Management lights on ?

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                        • #13
                          not aware there are 2 I changed the one by the exhaust cover.no lights on

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                          • #14
                            Yes there are two. Pre cat and post cat . You will need to get under the car to see it .

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                            • #15
                              many thanks I'll take a look

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