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Thread: Rough Idle

  1. #1
    MYKEY's Avatar

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    Rough Idle

    Evening all..

    I'm hoping for some advice with a rough idle along with three fault codes my car has developed.

    13 Inlet temp sensor

    14 Throttle position sensor

    21 Temperature sensor

    Also the AFR ratio is all over the place at idle and when driving.

    Any help would be much appreciated

    Screenshot_20200212-230619.pngScreenshot_20200212-230654.pngScreenshot_20200212-230507.png

  2. #2

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    Hi Mikey

    According to the wiring diagram i have the O2 sensor, engine coolant temp sensor, TPS and MAF all share a common ground on the ECU, terminal 92 via splice/junction 18. connector C40, which is a 22 pin plug. on the ECU. the pin in the 22nd pin on that plug.

    I would check the ground on whatever sensor of those you can most easily reach.

    Jake

    *edit*

    they are all also fed 5v from the ecu, possibly from the same supply internally. so check they all have sensible +5v supply too. could be one dragging down the others due to a fault.
    Last edited by Amonlym; 13-02-2020 at 07:34 PM.

  3. #3
    MYKEY's Avatar

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    Cheers Jake,

    I'll take a look, but i'm not too great on auto electrics so i may be back with some more questions

  4. #4
    Nick Mann's Avatar

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    Can you clear the codes? Battery disconnect should work.
    Rough idling and strange afr can be indicative of a boost leak too.

  5. #5
    MYKEY's Avatar

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    I'll clear and check again tomorrow Nick, i hope it is something as straightforward as a boost leak.
    If it's an electrical issue i'm probably going to have it looked at by the garage i use.
    Thanks for the advice Nick.

  6. #6
    Nick Mann's Avatar

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    Jakes info makes me suspect that you do have a grounding issue. But a couple of quick checks that are easier to do first still seems like a good idea.

  7. #7
    Davezj's Avatar

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    Mykey, have you disconnected the maf sensor with the engine running or ignition on.
    If so it will force error codes on Inlet air temp
    same applies for the throttle position sensor.
    and coolant temp sensor.

    i know some people like to pull electrical plugs off when checking for faults and actually force more error codes to b displayed than are actually causing any issues.
    but bad grounds will cause issues.
    in the past i had an issue with baro pressure sensor and throttle position sensor 5v supply raili shorting issue that cause violent acceleration loss when the gear box pinched the wiring loom against body and shorted the 5V supply to chassis ground due to bad engine and gearbox mounts. it took a while to track down the fault. but i tracked to down by monitoring all the sensor with evoscan when the issue occurred and then review the log files to find out which sensors had issues at the time of the fault. so you could try that method of fault finding.

    Bye for Now!

  8. #8
    MYKEY's Avatar

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    Hi Dave,

    No, I've not disconnected anything.... yet
    I have Evoscan but i need a tutorial on how to use it, their website isn't that good for beginners and hasn't been updated for a long time.

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    I had a rough idle, I went through all sorts of cleaning including the stepper motor, I then focused on on the coil packs, reconditioned them, and did some head scratching, replaced all my vacuum lines, and noticed it was a rough idle sometimes, but others it was fine and there was also a stutter at 4500rpm, id discounted the spark plugs as they were gapped correctly and iridium 7000 miles approx. but after pulling the rear plugs, hey all showed signs of needing to be replaced, I got a new set and all was well

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    EGR Location

    Hi. Could anyone tell me where the EGR valve is located in my VR4 Legnum 1997. Preferably with a picture. My car runs rough and dies on revs about 2000rpm. Any help would be appreciated.
    Dresider

  11. #11
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    Quote Originally Posted by Dresider View Post
    Hi. Could anyone tell me where the EGR valve is located in my VR4 Legnum 1997. Preferably with a picture. My car runs rough and dies on revs about 2000rpm. Any help would be appreciated.
    Dresider
    There isn't one.

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