1. Crazy trouble code mysterys p0300 and p0344 and p0303

    07 wrangler jk 3.8l
    it all started with a p0301 code, misfire cylinder one so I replaced the spark plug for cylinder one then I got a P0303 code so I replaced all of the spark plugs and all of the spark plug wires.

    The code then changed to a P0300 misfire in random cylinders. so I replaced the camshaft positioning sensor. The code went away for about a month and then I received a code P0344, camshaft positioning sensor circuit interruption.
    and then that was soon followed by the misfire codes again.

    any ideas of what could cause this?
    and where I should go next for fixing it?

  2. #2
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    Crazy trouble code mysterys p0300 and p0344 and p0303

    How-did the plug #1 look when you first replaced it?
    With random moving codes always start by looking at your battery. Checked the battery voltage is 12.4 off and have it load tested. Then clean the connections to the battery in the battery terminals. Then clean the opposite ends of your grounds where they connect to both the engine and the chassis. Dont forget to inspect the wires themselves for corrosion. Many times a bad wires, connections or a bad battery causes random codes.


    Never look down on anyone unless you are helping them up - Jesse Jackson
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

  3. #3

    Re: Crazy trouble code mysterys p0300 and p0344 and p0303

    The plug looked old and a little dark, but not too terrible.
    ah another symptom that has started with this is, random engine shuts off. Like I got to the top of a long hill near my house, when I crested the hill and stopped at the light, I stalled right in the middle of the street.
    and it wasn’t like a jerky stall, I didn’t even know I had stalled until I went to hit the gas and nothing happened.

  4. #4
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    Crazy trouble code mysterys p0300 and p0344 and p0303

    Were the other plugs the same or much cleaner?

    Do you hear/feel the misfire?

    If they are all the same id start by checking fuel pressure. Key on, at idle and at app 3k or above. Pressure should be constant and no bouncing or jumping.
    The only other items are the ckp that is the crank shaft position sensor and the coil pack. The ckp works in conjunction with the cam sensor to set timing. The crank shaft sensors have been known to just fail and not set a code.
    The coil packs also fail.

    Any other codes or sets on a diagnostic reader?

    Never look down on anyone unless you are helping them up - Jesse Jackson
    Last edited by JPNinPA; 09-18-2021 at 09:40 AM.
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

  5. #5
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    Re: Crazy trouble code mysterys p0300 and p0344 and p0303

    So you have an older thread on this. I read through it.

    There are internal issues that can cause misfires to get an idea without ripping it open you will need to do a compression test and leak down test.


    Never look down on anyone unless you are helping them up - Jesse Jackson
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

  6. #6

    Re: Crazy trouble code mysterys p0300 and p0344 and p0303

    So I changed the cam shaft sensor and the issue went away for about a month and now it’s back.
    and I the Jeep randomly stalls at low RPMs.
    like after I come to a stop after being on the gas.
    like drove up a long hill and down the other side and when I came to a stop light, after a few seconds of sitting there the Jeep just shut off.
    it didn’t jerk or sputter just quietly shut off.

    i never hear a misfire or feel it at all.

    where do I tie in to the fuel line on a 3.8l to check the fuel pressure?

  7. #7
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    Crazy trouble code mysterys p0300 and p0344 and p0303

    You have to install a Schrader valve.

    Check the connector to the TPS




    Never look down on anyone unless you are helping them up - Jesse Jackson
    Last edited by JPNinPA; 09-24-2021 at 08:27 PM.
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

  8. #8

    Re: Crazy trouble code mysterys p0300 and p0344 and p0303

    Ok I can pick up one of those harbor freight kits, and some fuel hose.
    should I do it like in the video, just crank the engine?
    or should I start it and let it run while I check the pressure? Or both?

    also, what is the fuel pressure supposed to be on a 3.8l v6 wrangler?

    i read somewhere that I have to unplug the fuel pump and run the engine until it stalls to de pressurize the lines before I install this tester, is that true?

    thanks for all your help so far dude

  9. #9
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    Crazy trouble code mysterys p0300 and p0344 and p0303

    If you set it up like them use clamps to hold it on at each connection. Run the engine so there is fuel in the line. Test these conditions

    Key on.
    Engine ideling
    Engine rpm - between 3000 - 5000 rpm

    The needle should stay constant. No large bouncing.

    Spec 58 psi +/- 2psi

    PS you likely could borrow a fuel pressure gauge. It might not have those nice adapters.

    Never look down on anyone unless you are helping them up - Jesse Jackson
    Last edited by JPNinPA; 09-25-2021 at 08:29 PM.
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

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