Replaced coils and plugs but still have a misfire????

[krzybtch]

Is there something else I need to do to fix the misfire?? 02 Jeep Liberty 3.7ltr

 

[ltd02]

What cylinder is the problem?

 

[krzybtch]

I believe it's 2 because when I removed the old plug, the ceramic around the pin was completely gone and it was totally black

 

[LibertyTC]

It is best to use the correct spark plug terminology.

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The correct spark plugs for the KJ is NGK ZFR6F-11G set electrode gap at .040 inch.
The coil pack should also contain the rubber o ring seals as well.

 

[ltd02]

Did you get a cylinder specific engine code? Should throw a P0302 for cylinder #2. What do the other plugs look like? Did you change all the coils and plugs?

 

[krzybtch]

Yes I changed them all I haven't put it on a code reader I'm just assuming because of what the plug looked like. Is the gap supposed to be at 0.40? Because I was told something else by autozone

 

[ltd02]

Like LibertyTC said gap should be around 0.04". That's what the sticker under the hood called for with the copper core plugs. I ran that gap too but some will say 0.035 to 0.044. Opinions vary and it may vary with different types of plugs.

 

[Dave_too]

You may want to also check the coil on that cylinder for damage. It can potentially present as (a) very thin linear crack(s). Myself, I prefer Delphi (I've had trouble with OEM coils in the past.) for replacement and if it comes to that, after you locate the real source of the issue it's time to replace them all. If you've done everything previous folks on this thread have recommended and gotten nowhere, it's time to have someone stick a camera in there.

 

[uss2defiant]

1. you can use the key trick to look at the CEL codes
2. Check the resistance of the coil. I think i posted that in the past or autozone would have the info for that. or you can play musical chairs on the coil and see if the problem follows the cylinder.
3. given that the ceramic part was missing, did any fall in the cyliner? perhaps using a borescope to check. Apparently it's part of autozon loaner tool. https://www.autozone.com/loan-a-tools/loaner-borescope-inspection-camera

 

[krzybtch]

Thanks for all the help, I regapped the plugs to 0.040 and it's running great. I just have to get an exhaust leak fixed and it should run perfect. Thanks again