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Thread: Low idle when warm (engine's cut out once) - Boost leak test advice needed.

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    Low idle when warm (engine's cut out once) - Boost leak test advice needed.

    Hey guys, so my Legnum has a low idle when the engine is hot. It starts perfectly fine when cold but the idle drops to around 600 when warm and the engine has cut out once when coming to a stop at an island. Under acceleration the car is totally fine though.

    I’m planning on doing a boost/vacuum leak check at the weekend before I start troubleshooting parts so I’m looking for some advice on that process. I’ve got a bung made for the compressor hose and have an air regulator on the way. Do I need to add a bung to another part of the system to pressurise it whilst I check for leaks?
    I’ve watched Mark’s video on YouTube so it looks like I need to remove the hard Y pipe to add air down by the washer bottle. Would I need to blank off any other parts of the system?

    Also, I have a TurboSmart manual boost controller with a built in bleeder valve so I’d imagine I’d need to remove that too?

    IMG-20171120-WA0003.jpg
    Last edited by sayn117; 12-02-2018 at 02:14 PM.

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    Nick Mann's Avatar

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    Add air where you have suggested, 1.5 bar should be loads, and listen for leaks. You will need to leave air trickling through. There is no need to blank anything else off.

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    Cheers for the info Nick. The boost controller is set to 1 bar so should I just remove that whilst doing the leak test?

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    There shouldn't be any need to remove anything. You are going to want to be testing it under the conditions you are driving it.

    Even if you can't hear anything, go round all joints between your bung and the pistons with a spray bottle of soapy water and look for bubbles.

    However, what you're describing may be a larger leak, or it may be a failing/incorrectly reading engine coolant temperature sensor - someone else had poor idling with due to this, and it's a ~£15 part and only a few minutes to replace.

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    Nick Mann's Avatar

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    It could also be a vent to atmosphere dump valve with a soft spring or a little leak.

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