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Multiple cylinder misfires after having just changed spark plugs, coil pack and fuel injectors

Discussion in 'Cherokee' started by Richardxj2001, Sep 14, 2021.

  1. Sep 14, 2021 at 4:14 PM
    #1
    Richardxj2001

    Richardxj2001 [OP] New Member

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    Ok not even a month ago I replaced the spark plugs the coil pack and this past Sunday I just changed out the fuel injectors. I was driving home from work today and I got a code on my obd2 scanner saying that I have multiple cylinder misfires and I just changed the spark plugs coil pack and fuel injectors. I’m at a loss on what else that I have to do to get rid of the miss fires and stop the check engine light from coming on? Any help would be greatly appreciated
     
  2. Sep 14, 2021 at 5:12 PM
    #2
    aggrex

    aggrex Well-Known Member

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    Prior to installing all the new parts was there a misfire or any issue that triggered the need to replace parts. Did you use OEM plugs, OEM injectors, OEM coil pk etc? Sometimes using off brand or non OEM parts can cause these issues. These questions may help others chime in with suggestions
     
    Bob and Awrench like this.
  3. Sep 14, 2021 at 7:53 PM
    #3
    Richardxj2001

    Richardxj2001 [OP] New Member

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    After 2 weeks of owning the Jeep it had a miss fire on number 2 and number 5 Cilinders so as I was told to change out the coil pack the spark plugs and the fuel injectors. I got the coil pack from Napa so don’t know if it was OEM or not and the spark plugs were from Napa as well and they were the champion gold spark plugs that are what the xj like to use from what I’m told and what they had in them in factory as well. The fuel injectors I got from auto zone and there Duralast brand so don’t know if they are OEM or not as well drove the Jeep to work it was fine no check engine light and then on the way home I got about more then half way home and the check engine light came on and would flash I hooked up my obd2 scan tool and that’s when I found out that the miss fire was coming from 2 3 4 5 Cilinders after replacing fuel injectors after I replaced the coil pack and spark plugs before the fuel injectors got replaced. A P0300 did come up in the codes as well with the p0302 p0303 p0304 p0305 no miss fires on 1 or 6. I did change the parts to fix the first set of miss fires which was only on 2 and 5.
     
    Last edited: Sep 14, 2021
  4. Sep 14, 2021 at 8:09 PM
    #4
    Groundfault

    Groundfault Well-Known Member

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    P0300 ? Any others codes?
    Like @aggrex said. Did you change parts to fix a misfire?
    Lots of potential causes for multiple cylinder misfire including the plugs, coil and injectors.
    Spark plug wires
    Vacuum leak
    Low fuel pressure
    Camshaft sensor
    Crankshaft sensor
    I'd check some of the other stuff before buying sensors.
    Plug wires if they're high mileage.
    Put a vacuum gauge on it, should be in the 17-21" hg range.
    Check fuel pressure when running, should be 44-54 psi.
    Best of luck and keep us posted.
     
  5. Sep 14, 2021 at 8:21 PM
    #5
    gowenby2002

    gowenby2002 Member

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    Hi, sorry you are having this problem too, as I had this problem with my 4.0 inline 6 cylinder(2002 tj). I had changed coil bar, plugs, ignition sensor, and random misfires occurred randomly (usually upon hard acceleration and/or higher speeds or both, usually both. Lived with this for sometime. It would sometimes go into limp mode, and have to slow down and drive easy for check engine light to go out and resume normal operation. Finally, I replaced the coil bar again and have not had that issue anymore(guess it is a better quality coil bar). Anyway, maybe this helps you as it straightened mine up.
     
  6. Sep 19, 2021 at 1:28 PM
    #6
    Richardxj2001

    Richardxj2001 [OP] New Member

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    Ok update on Jeep there is no vacuum leaks compression is fine fuel pressure is fine. Check engine light doesn’t come on when I drive to work but only on the way home from work bought a new crank sensor today and once I got home found out that the crank sensor only has one bolt in it. So another question I have will only having one bolt in the crank sensor make the crank sensor act up or throw the engine off? Now I drove it to the parts place and for an hour around my town and still no check engine light on and even after driving for an hour and then back home no check engine light even hooked up the obd2 scanner and it said there was no codes for missfires. It only happens when I drive home from work driving to work no check engine light comes on only on the way home from work it will come on. Also I think my valves need to be cleaned as well and recommendations on how to clean them with out taking the head off? But that’s the update on the Jeep for all those that helped me out with checking it out but I’m really thinking it is the crank sensor that might be causing the issue any other things I need to look at at please feel free to let me know. And I want to say thank you to everyone that gives me ideas and other things to look at as well this is a great community
     
  7. Sep 19, 2021 at 10:19 PM
    #7
    gowenby2002

    gowenby2002 Member

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    As far as cleaning the valves (intake) you can try the old secret sauce (Marvel Mystery Oil). Take the air intake pipe off where it goes into the air intake manifold, with the engine running, slowly pour a bottle in while keeping the engine idled up, that is slowly, as not to let it choke down. It will really smoke a lot, a LOT! after finishing the bottle, leave running, re-install intake pipe, (be careful with engine running) and drive normally, the smoke will stop in a few minutes. This has looooong been an old time way to clean valves and unstick stuck valves. Can also add some at oil changes and into fuel. Just check the label. May be others can give you better advice, but this method has been used for many years.
     
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