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1997 Lexus LS400 Question: why the engine idles up and down ?



provost, Port Arthur, TX, October 30, 2009, 01:02

when the car is in park the engine will idle up and down, in gear it runs smooth but at a high idle, I changed the mass air flow sensar. What is causing this please ?

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  • Answer #1

    October 30, 2009, 11:42

    You could have a vacuum leak, or something else that is effecting the air/fuel mixture. There is an idle valve that controls the idle speed, this valve or the circuit that controls it may be having problems.
    I suggest you have this diagnosed before replacing any more parts though, the idle valve alone is over $500!

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    Visitor, February 09, 2011, 23:30

    thank you for your answer,i brought to dealer they say ecm and short circit,i replace ecm,air mass sensor and whole engine still the same,please help

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