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  • Idle speed

    Have you guys noticed that the idle speed is increased when you're in the mountains ? I noticed it last weekend when I was up around 1000m ASL and the idle was around 850 rpm , where it's 700 around sea level ?
    Cheers
    Ross

  • #2
    Did you stop and start the engine at all when you were up the mountain?

    Reason being the engine management system calibrates itself to ground level
    when you start the car, and as you climb this might upset the fuel mixture a bit if the car
    hasn't been restarted , but I would have thought the idle speed would detected from the engine RPM's.

    At high altitudes the ECU will also advance the timing and this would probably cause the idle speed to increase slighty if the throttle idle position was fixed. These days though most cars have ISC (idle speed control) to keep the engine idle speed constant with varying engine load conditions, ie air starting and stopping, lights on and off etc. Therefore it maybe for emission control purpose of some reason?

    Cheers
    LeighW
    LeighW
    Avid PP Poster!
    Last edited by LeighW; 06-10-2011, 12:02 PM.
    HKB Electronics, manufacturer of the Alternator Voltage Booster, Silver 2008 D4D,Lifted,Underbody protection, Alternator Voltage Booster, Tiger Z winch, Lightforce DL, Air Horns, Tanami Drawers, Drop down fridge slide, Outback cargo barriers, Rotronics dual Battery system, Polaris GPS, HF/UHF/VHF, Radio speaker combiner, Long ranger water tank, Diff breathers, Inverter, Snorkel and others

    Comment


    • #3
      Leigh
      Yes I did start and stop as I was camped in the mountains near Bathurst . It might also have been due to the cold temp which was in the single digits .
      Cheers
      Ross

      Comment


      • #4
        Yes, it is normal. Even in my 120 Prado. Air is thinner at higher altitude so RPM increases to compensate. There is a noticable loss of power also.

        Comment


        • #5
          My 150 currently idles between 800 to 900. It sounds to high for me. Is this right.
          I noticed today as I was idle down a track in high and I had to keep riding the brakes to keep it slow enough.

          Thank you.
          SOL.
          [COLOR="#006400"][url]http://www.pradopoint.com/showthread.php?26339-SOL-s-150-shorty-SX[/url][/COLOR]

          [COLOR="#00FF00"]4wdriving[/COLOR] [COLOR="#0000FF"]First Party[/COLOR] - [COLOR="#FF0000"]Bitumen: A Blatant Waste of Taxpayers Money![/COLOR]

          Comment


          • #6
            Hey SOL,
            I just had the same experience. Climbing up a hill in L2nd for approx.100m. Once at the top the rpm kicked up just under 1K rpm & wouldn't settle even after 5min; on the brakes all the way down the other side in L1st. Not a very comfortable feeling. Buggered if I know why it wouldn't settle back to my usual 850rpm??

            Comment


            • #7
              Probably something to do with antipollution control.
              HKB Electronics, manufacturer of the Alternator Voltage Booster, Silver 2008 D4D,Lifted,Underbody protection, Alternator Voltage Booster, Tiger Z winch, Lightforce DL, Air Horns, Tanami Drawers, Drop down fridge slide, Outback cargo barriers, Rotronics dual Battery system, Polaris GPS, HF/UHF/VHF, Radio speaker combiner, Long ranger water tank, Diff breathers, Inverter, Snorkel and others

              Comment


              • #8
                SOL, you didn't by any chance hit the idle up button did you?
                The missus drove the prado to the shops the other day and was complaining the engine was idling high when she got there, turns out she hit the idle up by accident.

                Comment


                • #9
                  Andrew, No my idle up does not seem to work. I tried pressing it o no avail.

                  SOL

                  Originally posted by Andrew119 View Post
                  SOL, you didn't by any chance hit the idle up button did you?
                  The missus drove the prado to the shops the other day and was complaining the engine was idling high when she got there, turns out she hit the idle up by accident.
                  [COLOR="#006400"][url]http://www.pradopoint.com/showthread.php?26339-SOL-s-150-shorty-SX[/url][/COLOR]

                  [COLOR="#00FF00"]4wdriving[/COLOR] [COLOR="#0000FF"]First Party[/COLOR] - [COLOR="#FF0000"]Bitumen: A Blatant Waste of Taxpayers Money![/COLOR]

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                  • #10
                    I believe the idle up only works to assist with warming the engine and once the engine reaches full operating temp it effectively turns off and has no effect.
                    Stephen Bloomer
                    I did have - 2010 GXL D4D Auto, ARB bullbar, rails, sliders, winch, 40mm lift, Brown Davis bash plates and long range tank

                    Comment


                    • #11
                      Smakb, That makes sense then. It does not get cold enough here to need warming.

                      SOL.

                      Originally posted by smakb View Post
                      I believe the idle up only works to assist with warming the engine and once the engine reaches full operating temp it effectively turns off and has no effect.
                      [COLOR="#006400"][url]http://www.pradopoint.com/showthread.php?26339-SOL-s-150-shorty-SX[/url][/COLOR]

                      [COLOR="#00FF00"]4wdriving[/COLOR] [COLOR="#0000FF"]First Party[/COLOR] - [COLOR="#FF0000"]Bitumen: A Blatant Waste of Taxpayers Money![/COLOR]

                      Comment


                      • #12
                        Hey LeighW,
                        I still have this annoying issue with the increased rpm once seemingly 'hot'. Whats the connection with your anti pollution suggestion, can this effect idle speed?
                        Cheers

                        Comment


                        • #13
                          Certain conditions may cause engine RPM increase ie ECU thinks fuel vapor may occur, exhaust emission have gone out of spec (fuel injector leaking) or maybe even engine over temp.

                          You may also have a faulty MAP sensor, whenever you start your car the engine management systems does and atmospheric pressure test, this sets the base line for the fuel mapping.

                          As you go higher the ECU remaps the fuel ratio, ie the higher you go the less air therefore the engine needs less fuel, only really going to be an issue at high altitudes. If for some reason the fuel for instance is not leaning out the ECU will detect high exhaust emissions and possibly increase idle speed to try and compensate.

                          Could also be a faulty temperature sensor, if only happens when engine is hot.

                          The only thing that will cause idle speed increase in a diesel is more fuel, so the engine ecu must be adding the fuel, the big question is why?

                          Leigh
                          HKB Electronics, manufacturer of the Alternator Voltage Booster, Silver 2008 D4D,Lifted,Underbody protection, Alternator Voltage Booster, Tiger Z winch, Lightforce DL, Air Horns, Tanami Drawers, Drop down fridge slide, Outback cargo barriers, Rotronics dual Battery system, Polaris GPS, HF/UHF/VHF, Radio speaker combiner, Long ranger water tank, Diff breathers, Inverter, Snorkel and others

                          Comment


                          • #14
                            Originally posted by LeighW View Post
                            You may also have a faulty MAP sensor, whenever you start your car the engine management systems does and atmospheric pressure test, this sets the base line for the fuel mapping.

                            As you go higher the ECU remaps the fuel ratio, ie the higher you go the less air therefore the engine needs less fuel, only really going to be an issue at high altitudes. If for some reason the fuel for instance is not leaning out the ECU will detect high exhaust emissions and possibly increase idle speed to try and compensate.
                            Yarp. About sums it up. We used to have issues with MAP sensors all the time in Alaska. They would fail and as our altitude climbed higher and higher we would often find vehicles stalling out because they wouldn't idle up.

                            Comment


                            • #15
                              Will just throw into the pot as I'm sure you've already considered it, the aircon
                              when compressor is running will speed the idle up about 150RPM.

                              Leigh
                              HKB Electronics, manufacturer of the Alternator Voltage Booster, Silver 2008 D4D,Lifted,Underbody protection, Alternator Voltage Booster, Tiger Z winch, Lightforce DL, Air Horns, Tanami Drawers, Drop down fridge slide, Outback cargo barriers, Rotronics dual Battery system, Polaris GPS, HF/UHF/VHF, Radio speaker combiner, Long ranger water tank, Diff breathers, Inverter, Snorkel and others

                              Comment

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