Question about 2003 Mercury Grand Marquis

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The car has a slight **** (almost like a missfire) check engine light does not come on.runs perfect for miles then a little miss or two and its fine I can press the gas to the floor and the car takes off.All plugs and coils where replaced

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  • bmdks Jul 21, 2009

    Filter also was changed

  • bmdks Jul 21, 2009

    tried a few different brands also been using high test gas, seems to be a little better since the problem began



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Check the EGR/DPFE sensor. They are all one piece for the 03 and newer models. I had the same problem and after replacing inectors,coils and plugs I still had the problem. If there are no vacumn leaks then this may be the problem. Try to clean the EGR and MAF sensor and if the EGR is really bad then look into the OEM replacement part since alot of aftermarket units trigger Check engine light. Try to search for DPFE problrms online and you will see that this is a common problem.

Posted on Aug 16, 2009

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Sounds like a clogged filter........most likely to be the inline fuel filter, thats the one just before the fuel pump

Posted on Jul 21, 2009

  • jim galbraith
    jim galbraith Jul 21, 2009

    have you tried fuel injector cleaner....the additive type thats added to your fuel, this cleans deposites in the injectors.....(..small tip..), always use more than the manufacturer older engines need a little more persuation................

  • jim galbraith
    jim galbraith Jul 21, 2009

    try some heavy duty engine flush, but after you start your engine, run it to normal running temp.......then run you engine at 3000 RPM..for 2mins...( sore on your foot,but worth it )....then switch off, and restart straight away, and run engine normaly..........



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