Ford Mustang Has A Rough Idle

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  • #15854 Reply

    Trevor Swinney

    3.8L V6 Mustang idled rough so I changed spark plugs, spark plug wires and coil pack ran good for a bit and took care of some of the rough idle but now acts like there is nothing under the hood at 65 it will get up and go but anything before that it takes a while to get up the rpms and speed.

  • #15858 Reply


    A rough idle is usually caused by a vacuum leak. If changing these ignition parts fixed the rough idle but know it has a new problem of poor acceleration, i would re-check the spark plug gap.They normally come set already, but that does not mean they should not be checked before installation. Also have the fuel pressure checked.

    • #15859 Reply

      Trevor Swinney

      Thank you I was thinking about checking the gaps and I will look into the fuel pressure what is the best way to check that???

    • #15860 Reply

      Trevor Swinney

      I took out all the spark plugs and gaped the ones that were not at 54 to 54 and saw a different coil pack diagram and switch the wires to that diagram and it runs a lot better but I still have a cylinder 2 misfire So I ran a compression test on test on it and came out with around 120 but the question is i don’t know what causes that one cylinder to misfire checked for vacuum leaks and everything is good except that 2 cylinder.

  • #15876 Reply


    Compression is good. As long as you are sure you got the plug wires on the correct cylinders now and that cylinder is getting spark, then check for a bad fuel injector. It can fail electronically- open circuit inside or high / low resistance, or it can be plugged so no gas is flowing from it.

  • #15880 Reply

    Trevor Swinney

    Got it fixed idk what it was but changed wires 1 and 2 on the plugs and the 1and 2 spot on the coil and it fixed it idk what changed.

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