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  1. #1
    Wranglermudder2011's Avatar
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    Cylinder 4 misfire

    Hi my names craig i have a 97 wrangler with the 4.0 i6 engine with auto transmission i have a check engine code of p304 for cylinder 4 missfire and a code for my o2 sensor in bank one reading to lean how can i fix my missfire it has new plugs wires cap rotor and coil and has just over 237000 miles

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    JPNinPA's Avatar
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    They may be related. Check #4 plug that it is snug. Swap #4 injector with another cylinder. See if the issue follows clean/replace the injector or verify the seals are good. It could be a vac leak or a dirty injector.
    Last edited by JPNinPA; 03-20-2014 at 01:38 AM.
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    Okay thank u ill try that and get back to u guys

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    Another thought. The too lean code could be an exhaust leak at or before the downstream O2.
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    Is that the fist 02 and i do have a leak right after my manifold i have an aftermarket banks tourgue tube power catback exhaust on it and the plates for the bolts to attach it to the manifold it disnt come with a new one so the bolts pulled threw the rust i was gonna work on gettin that fixed its a banks header to 2 3/4

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    Oh and i re scanned the codes today the 02 sensor code is still there but its throwin a camshaft possition sensor code but i dont have a camshaft possition sensor on that engine

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    The sensor is in the distributor.
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    For the cam on the 97 4.0 so i gotta change the distributor cause the only thing they bring up for the cam sensor at auto zone i a fiber disk?

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    Re: Cylinder 4 misfire

    the fiber disk is a spacer for the sensor in the distributor, replace the whole thing and do the crank shaft sensor as well. When one starts going it seems to cascade on my 01. So I started replacing both as a pair.

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    Thanks for the tip

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    Re: Cylinder 4 misfire

    I cant get the disk today gotta get it tomorrow its 3 bucks the sensor was 43 though i got it gonna get back to u guys with it tomorrow after my shift and give yunz an update thank u

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    I changed the sensor there was disk under neith it or around it at all it seemed to take the miss away but it still does some funny studder threw driveing rang any ideas about that problem?

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    Did you reset the CEL? You do this by disconnecting the battery for a few seconds. I turn the key to start the engine while disconnected to bleed any stored charges. This should clear the cell. If the cel comes back within the next three to five starts the issue is still there. If so goth advanced, Az, or OReilly's .

    For the shutter while increasing speed there are a few easy things that need to be done every once in a whille,

    1) Clean your battery terminals. Clean the grounds at the engine and chassis.

    2) Clean your Throttle Body and Idle Air Control.

    3) verify you spark plug gaps, wires and snug plug insertion.

    4) Actuate, clean or replace the throttle position sensor.

    5) If you still have the O2 cel this will cause issues. What is the actual code? Fix the leak or replace the sensor based off the actual code.

    What spark plugs are you using? Brand and part number.
    Last edited by JPNinPA; 03-23-2014 at 08:58 PM.
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    I havent had the chance to check the codes again amd it came on after about 8 miles of driveing and but i did reset it bye disconecting the battery but i didnt turn the key on and the exhaust is fixed and completly sealed off from the head to the end um i checked and cleaned a few grounds theres one on my coil to my frame thats questionable its still attached but not as well as id like it to be kinda frayed at the frame side battery is new and termernals are really clean and wires are good two but im a try and get the codes scanned asap and ill get back to you

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    And idk the part number off hand on my plugs but i think there ac delcos or a cheaper brand like that and they only have bout 650 miles on them

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    Quote Originally Posted by Wranglermudder2011 View Post
    And idk the part number off hand on my plugs but i think there ac delcos or a cheaper brand like that and they only have bout 650 miles on them
    Milage on the plug or age doesn't matter. Poor performing plug will be a poor performing plug. You need single platinum plugs gapped to 0.35 . Autolote and champion make a good plug that is not too expensive. You could also run double platinum or iridium plugs with no issues. The iridium plug is expensive but are much longer lasting plugs.

    Ap985
    App985
    Xp985

    3034
    7034
    Last edited by JPNinPA; 03-24-2014 at 10:17 AM.
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    Will have to look into that thank u i was always told the bosh platniums and such are bad to run in the i 6 its better to use the cheaper plugs but ill look into that thanks

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    Re: Cylinder 4 misfire

    Do you still have the vac leak on the manifold, or did you already fix that?? Vac leaks will make it run all sorts of funny, and nothing will correct it except fixing the leak.

  19. #19
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    Ya i fixed the exhaust it leaks a little back bye the muffler but its not bad

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    Quote Originally Posted by Wranglermudder2011 View Post
    Ya i fixed the exhaust it leaks a little back bye the muffler but its not bad
    He means the intake. If you have an intake leak you could have a rough idle. To find this you could spray around the TB and intake near the cylinders with TB cleaner and listen for the engine rpm to change.

    What rpm do you idle at?
    Last edited by JPNinPA; 03-25-2014 at 01:04 PM.
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