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cam shaft

by chaz_bentley on Jun 30 2017, 1:28 PM

I have a misfire on a 98 mustang GT. but all injectors, coilpacks, and spark plugs are working properly. could it be a bad cam lobe??

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13 Replies
  • By 1986chevyman

    Hook up a vacuum gauge and bring it  up to 2000 RPM and observe the needle on the vacuum gauge.

    If it is bouncing around a lot, you most likely have a valve sealing issue, like a broken valve spring.

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  • By sprintwrench4x
    pull valve cover and check valve springs...dollar to a donut, you have a broken spring . but first take compression test of all cylinders.
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  • By whittyjak
    pull the valve covers off and measure the cam lift.
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  • By whittyjak
    pull the valve covers off and measure the cam lift.
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  • By jeffreyd1
    What test procedures were performed to verify all coils, plugs, & injectors are working properly. In the last couple of weeks, we have gotten bad Motorcraft plugs out of the box on 2 different occasions w/different vehicles. I hope you are scoping injector & coil patterns(while it is misfiring). Are you able to ID the cylinder that is misfiring? Compression is a good test to perform, but do not assume that if you replaced a part it is good either.
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  • By racingkain1071
    I don't mean to sound like a broken record repeating what people have already said, but a compression test and pulling the valve cover off and checking the springs, retainers, and rockers would be the best place to start right now. 
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  • By 84elky383
    Yeah I would agree with compression test, would be able to compare every cylinder maybe even take off valve covers and check to see if anything is broken like rocker arms, springs ect. I wouldn't think its the cam but it could be maybe double check everything else.
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  • By 1969mach1

    Are you getting misfire codes? You may need to get it to someone with a good scan tool ,they should be able to pinpoint the cylinder that the problem is in and then they can see if its an electrical problem or not then if no problem there ,look at mechanical issues like valvetrain problems.

        

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  • By fordtek1
    any noise in engine? I've seen these 4.6's pop off rocker arms before.  First, I 'd use a noid lite and see if pcm is giving the signal to "fire" the injector, if good, Id run a compression test and possibly pull the valve cover if need be. 
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  • By vulctech1
    miss at idle , under load ? worse hot /cold? whats the vacuum reading (first indicator of mechanical problems like that ) . only at startup ? coolant leaking in ? could be anything , need way more info and testing first
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