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Thread: Idle issues

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    rajvr497's Avatar

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    Idle issues

    Hey guys , so as stated above I'm having some idle issues with my friends vr4 , the issue we are experiencing is the idle won't go lower then 1400 rpm when up to temps and the idle screw is already backed all the way down ....

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    may be a sticking IAC valve. Have you tried cleaning the IAC valve ?. Try unplugging it to see if the RPMs change. You may get a check engine light after removing the IAC valve connected but a battery reset will get rid of that.

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    could also be a major vacuum leak on one of the hoses or a bad gasket or a perished seal on the idle screw. Try plugging the idle screw hole with your finger (dampen for good seal) you will feel a strong vacuum if its letting by.

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    Davezj's Avatar

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    The idle screw on the throttle body is called the bist screw in the manual for reference and should be set in a particular way to enable the idle control valve to operate correctly.

    You should monitor the idle control valve in evoscan and adjust the bist screw to get a particular value on the idle control valve.
    This enables the the idle control valve to be at the mid point of its travel so when required the ICV can adjust the idle up or down. If the ICV is maxed out in one direction then it is unable to control the idle.

    I am not saying this is the issue, all I am saying is the bist screw should not be used for turning the idle up or down. It is required to be set correctly and it is all the tables in the ECU that sets the idle point via the ICV. If you raise the or lower the idle with the bist screw the ECU will try and adjust the idle to the value in the ECU until the ICV runs out of adjustment range.
    Last edited by Davezj; 29-03-2019 at 12:05 PM.

    Bye for Now!

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    rajvr497's Avatar

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    I changed the idle control this morning but now I realize the car isn't idling up at mornings anymore

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    I'll do a boost leak test as well ...

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    The Base Idle Screw in the throttle body should be set when the engine is up to operating temperature to the desired idle speed that the ECU is commanding, and the Stepper Motor is locked at 22 steps using the "Speed Adj. Screw Mode" feature in EvoScan (or the equivalent feature on a MUT-III).

    This is assuming that the stepper motor is functioning correctly, and there is no air leaks anywhere in the inlet path.

    However, as you've felt the need to mess with the screw, it's not, so you'll now need to fix/replace the stepper motor/leak, and readjust your idle screw, rather than just fix the stepper motor/leak issue.

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    I knew there was a proper procedure for this somewhere and it turn out the the procedure is in Garry . Lol

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    Once you're up to operating temperature, connect EvoScan (not sure if you *need* an OpenPort cable, or whether a cheap modified VAG-COM cable will be sufficient for this), and hit the "Speed Adj. Screw Mode" button in the bottom-right corner.

    idle.PNG

    The ISC Steps should then lock (from memory, the value is 22), and then adjust the screw until you're sat as close as possible to the Target Idle RPM (about 750)

    idlerpm.PNG

    Once you disengage the "Speed Adj. Screw Mode", the ISC should start adjusting to track the target idle RPM even closer.

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    Great info there I'm gonna do this in ah bit I'll follow your every step just in gonna set my idle to 900rpm in the ecu...thanks alot @GARRY

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    rajvr497's Avatar

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    Hey guys, so i did a boost leak test and came up with nothing car still idles at 1500 - 2000 rpm
    Tried unplugging the idle control same issue
    I logged idle control stepper motor and is on 82+ counts which is know is wrong
    Is there a wiring diagram for the idle control harness end just to make sure its not a harness issue ?

  13. #13
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    Raj, so when you lock the idle screw counts and adjust the ifele screw what happens?

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    Hi Guys,

    is this the cable I need to work with evo scan and set-up idle speed/servo?

    https://www.obdiitool.co.uk/wholesal...flsh-chip.html There seems to be 2 options I'm unlikely to flash my ECU myself so do I just need the cheaper option?

    Thanks
    Steve

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    Nope, don't buy a fake like that.

    These are so horrendous, that they require special drivers on your machine, if you connect to the internet with it plugged in it'll brick the unit and you're left with something not working. It's all kind of horrible.


    A £5 VAG-COM cable (with the FTDI chipset) modified as per HOWTO: Log from your ECU for less than £30 is the better bet.

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    Thanks, I've never soldered electronics. But I'll give it a go.

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    Only ones I can find online that mentions the FTDI chipset. Are these correct? Prices have gone up a bit. Do I need to buy evoscan too?


    https://www.ebay.co.uk/itm/281145698...EAAMXQdPxRnQJa

    https://www.ebay.co.uk/itm/281149386...3ABFBMnOafkfNf
    Last edited by CHESHIRECAT; 18-03-2022 at 12:15 PM.

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    Hi guys, I have been tryin to sort my idle issues today. I have the cable and evoscan. The car is upto temperature and running at 1500rpm. When I lock the idle speed actuator it drops to where it should be (650rpm) and I can adjust the speed. However as soon as I remove the lock, the idle speed returns to 1500rpm. Here are screen shots of evoscan when it is unlocked.
    Capture5.JPG
    Capture4.JPG

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    For some reason I am not getting diagnosis codes through evoscan also.

    Capture8.JPG

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    The initial screenshots are with the old idle speed actuator. I put the new one back on. The same thing is happening, idle speed is correct when locked but reverts to high when unlocked although at 1200 rpm.

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