Question about 2003 Mercury Grand Marquis

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241500 car hesitate at times /dianose someting to do with emissions

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  • Patricia McKinney
    Patricia McKinney Apr 14, 2014

    car is shuddering, like a skip; 4 plugs were replaced, but PC won't give a code, even when connected in car with tech in back seat, This is driving me crazy..

  • mountean May 08, 2014

    I would have to know what kind of car this is to be helpful. If it's a 4 cylinder then you *may be able to rule out the plugs. Next of course is wires, distributor, rotor, or an individual coil pack if your engine doesn't use a single coil.

  • mountean May 08, 2014

    As a side note sometimes plugs brand new from the factory are faulty. But if changing the plugs doesn't change the problem, they're not the problem. As a last guess, if the misfiring comes and goes at times, there may be water in your gas.



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That sounds like a sensor malfunction. It could also be because of a bad wiring connection. Check all your plugs and wires, especially any that are dirty. Also you can take it down to a local auto parts store and ask them to scan for codes, many of them will do it for free.

Posted on Oct 21, 2013

  • elmer d dawson
    elmer d dawson Oct 28, 2013

    took it too o'reilly trouble code p0456

  • mountean Oct 29, 2013

    Well there you go, I hope they told you what it means. I usually just look them up online if I don't know. The Haynes manual also lists them.



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