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Thread: Surging Disco at wot

  1. 9th July 2012, 08:23 AM #1
    uniland44
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    Surging Disco at wot

    Dear Land Rover enthusiasts,

    I have a Discovery 2, auto, TD5, 2003 (2004 model) that has developed an interesting problem. The car drives fine, fuel consumption is normal, no smoke, no loss of coolant, no overheating, no excessive play on the turbo spindle,... Just all fine.
    However, when I want to overtake a car and floor the throttle then the car starts surging badly. The same happens when I go uphill. Everything works just perfect until the point that the throttle is not more depressed then 60 to 70%.
    I thought it must be the turbo modulator (The solenoid with three hoses attached to it, PMK100130) as this is a common problem, so, I replaced it. I also replaced the airfilter and the hose between the turbo and the intercooler and removed the EGR. Still, the problem is still there. Performance wise everything is fine, even when I'm towing a 3000 kg trailer.
    Sometimes the problem doesn't seem to be as bad when I press the Sports mode button, but it's still there.
    I have a Hawkeye diagnostic tool and measured the manifold pressure as 219 kPa. I haven't got a reference to find out if this value is within the recommended range.
    There are no DTC's logged related to this problem. The readings on the MAF seem to be within specs as well.
    The only odd thing is that the reading of the turbo waste gate never goes higher then 7% (Whatever that means) (I had the Hawkeye plugged in whilst driving)
    Has anyone of you any clues where to start?
    Would re-setting the gearbox adaptations make a difference?
    What is the max turbo boost pressure on a standard TD5 engine?
    Your input and advice is much appreciated.
    Thank you and have a nice day,

    Luke
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  2. 9th July 2012, 09:49 AM #2
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    Barefoot Dave
    Barefoot Dave is offline Wizard Subscriber
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    G'day Luke.
    Sounds like classic over-boost. You are exceeding 1.2 bar and the ECM iscutting boost for protection. Feels like petrol engine rev-limiter?
    Locate the adjustment nut on the turbo wastegate actuating rod (the rod that connects the small can on the front top of the turbo assmbly into the body of the turbo and internal wastegate) and back it off a couple of turns.
    Funny, we have had a few threads like this recently, I guess the cold weather is contributing.
    Hope this helps,
    Dave.
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  3. 9th July 2012, 12:36 PM #3
    uniland44
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    Thumbs up

    Hi Barefoot Dave,

    Yes, it is like hitting a rev limiter on a petrol engine (albeit in slower cycles).
    I bought the car secondhand last year, so, somebody must have fiddled around with the factory settings. I used to have a Defender TD5 and this type hasn't got that waste gate modulator. As there are lots of threads about the before mentioned part I thought it wouldn't hurt to have it replaced.
    Thanks for your help and explanation.
    Luke
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  4. 9th July 2012, 02:50 PM #4
    thexprinter
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    Cool

    Quote Originally Posted by Barefoot Dave View Post
    G'day Luke.
    Sounds like classic over-boost. You are exceeding 1.2 bar and the ECM iscutting boost for protection. Feels like petrol engine rev-limiter?
    Locate the adjustment nut on the turbo wastegate actuating rod (the rod that connects the small can on the front top of the turbo assmbly into the body of the turbo and internal wastegate) and back it off a couple of turns.
    Funny, we have had a few threads like this recently, I guess the cold weather is contributing.
    Hope this helps,
    Dave.
    My problem started after fixing the exhaust studs (six were broken) as the vehicle was secohdhand ,I do not know what was messed with before. but backed off the actuating rod as descxribed sure fixed my surgeing problems... the x printer
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  5. 9th July 2012, 04:16 PM #5
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    Barefoot Dave
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    Luke, it seems that you threw away the modulator for doing its job, some thanks
    Maddening things, eh?
    Dave.
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