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Thread: d2a td5 auto surging

  1. 12th April 2015, 07:06 PM #1
    Acrabtree
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    d2a td5 auto surging

    hi guys
    so the d2a td5 auto is not being nice to me atm. The disco under harder than normal acceleration starts surging. I do not get the surging under normal driving conditions.
    I plugged the nanocom and found an overboost fault logged so I cleared that then went for a drive with the nanocom to watch the live readings.
    Whilst driving the turbo pressure did not go over 1.2 bar but still was getting the surging of overboosting. I also notice the wastegate signal was fluctuating from 6 to 9 to 2 under hard acceleration which led me to think the boost modulator was unserviceable. So I made the wastegate rod longer and went for another drive and watched the nanocom. I am now only getting 1 bar of boost but still have the surging issue.
    I then disconnected the MAF for troubleshooting purposes to find the car had no power at all and took forever to get up to speed so I reconnect the MAF and the power came back but still surging under heavy loads.

    Is there a way I can electrically test the boost modulator or am I looking in the wrong area???

    Thank you
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  2. 12th April 2015, 07:27 PM #2
    PhilipA
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    under hard acceleration which led me to think the boost modulator was unserviceable
    When It surged were you near max revs say 3900?

    If so it may be that your MAF is overreading and producing an implausible number (over 650+) and the ECM is converting it to zero.

    This was the problem with mine when I first bought the car.
    If this is the problem , if you do a dump of an acceleration run, you will see the dropout on the MAF curve.
    Regards Philip A
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  3. 12th April 2015, 08:01 PM #3
    discorevy
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    Do the run with nanocom , look at air flow readings when problem occurs , if readings are OK , then its probably boost controller , bypass this easily by running vacuum line directly from intercooler pipe to wastegate modulator, safe to do this until you can replace it ( about $45 ) , sometimes it can be cleaned with brake cleaner and compressed air but mostly requires replacing
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  4. 13th April 2015, 03:29 PM #4
    Acrabtree
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    Okay. Will have alook after work an troubleshoot more an get back to you's with the verdict.
    Thank you
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  5. 15th April 2015, 04:07 AM #5
    Acrabtree
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    So i went for a drive an watched the maf readings an they stayed steady. I then pull the turbo intake off an had alook at all the lines going to the boost modulator an found the hose going to the steel pipe exiting the turbo was almost rubbed thru. So i then replaced all hoses from the boost modulator an gave the modulator a clean with contact cleaner an now the disco is back to normal an hold a steady 1.12 bar of boost.
    Thank you for your help guys
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