New to KJ: CEL Misfire #4

[K9JEEP]

Hello all,

New to Jeep but not to wrenching on my own.

I purchased my 07 Liberty 3.7 with 38k miles (yes very low miles) 6 days ago and the CEL instantly came on before the first test drive. He said he had never had it on before. I took him for a respectable guy. We pulled the negative terminal to see if it would come back on and it didn't. Engine seemed to run fine, no noises or irregular shaking from what I could tell. Shifted smooth and seemed to have good power so I purchased it.

Drove home 60 miles and CEL did not come back on. The next day it returned. Got the code read at autozone and it was misfire in cylinder 4 and random misfire. I replaced all plugs with OE copper and all coil packs. CEL stayed off for 4 days and 75 miles or so then came back on. The car again drives ok, no noises of any kind, I feel a very slight hiccup at idle but thought it was normal for V6, I'm used to 4 cylinder turbocharged. All the reading I am doing is scaring me with the valve issues and springs falling and so on but I do not have the same symptoms as these people. The CEL does not flash, the car does not stall, I don't have any smoke.
I have not had this recent code read but will shortly.
The next thing I may try or swap with will be the injector if the code is the same.

Does anyone have any other suggestions for me, all will be considered. I am looking to drive this KJ for a long time and I really like it but don't want to get myself into a crazy hassle.

Thank you

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[HoosierJeeper]

What brand of coil did you use? Mopar is the best, aftermarket ones are iffy. Does it follow the coil if you move it around?

 

[K9JEEP]

Did not get Mopar packs, just picked them up from Autozone, I agree OEM is always best but was not going to throw money at something if it wasnt the actual issue. I didn't move them around to see if it followed yet. I just dropped it off at a trusted shop to have them take a look while I am working. I'd love to figure it out myself but like the fact that I can take it back to them if not solved

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[K9JEEP]

Got the Jeep back from the shop, they say nothing is wrong and it drives perfectly fine. The code was still saying misfire in 4 but seems to be OK. They said to continue to drive it and see how it is.

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[LibertyTC]

Pull the #4 spark plug and see what kind of plugs are in there and check the gap.
58449[/ATTACH]"]

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Jeep likes copper core NGK ZFR6F-11G not the platinums/iridiums and the gap has to be right .040.
Spark plug gaps get eaten quick with these intense voltage coil packs. Change them every 25 -30K miles.
Ya Mopar coil packs are best. I seem to be getting away with the Standard brand for now.

 

[K9JEEP]

Pull the #4 spark plug and see what kind of plugs are in there and check the gap.
[ATTACH=full]58451[/ATTACH]
Jeep likes copper core NGK ZFR6F-11G not the platinums/iridiums and the gap has to be right .040.
Spark plug gaps get eaten quick with these intense voltage coil packs. Change them every 25 -30K miles.
Ya Mopar coil packs are best. I seem to be getting away with the Standard brand for now.

Like I stated I put all fresh plugs in and gapped to 0.40. I could buy a new OEM coil and put it on 4 along with the other OEM coils and see if that helps.

If I simply disconnect the negative terminal on the battery the CEL would turn off but the code would be stored still so my question is would the CEL come back on for a code that was stored and not cleared vs a new code? Could there not be a misfire but the CEL came back on because the previous code was not cleared?

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[LibertyTC]

Ya sorry musta missed the OEM plugs replacement/ 040 gap.
You can see the live misfires on high end scanners.
58452[/ATTACH]"]

You must be registered for see images attach

Provides a count in live time, gives you an idea how bad it can be.
Mine was misfiring at part throttle 1650-1700 rpm and you could feel an engine shake, and then see it live.
TPS was sticking a bit due to worn tang in rear of TPS.
Throttle plate was also slightly binding, dremel polishing took place.
Might be worth a try to get one new mopar coil on #4
Fuel injector electronic pulses can be viewed on high end scanners if someone knows what they are doing as well.
I had no engine light. It takes a lot of misfires for it to turn the light on.
Ya clear the code and then run /drive it after clearing.

 

[K9JEEP]

Ya sorry musta missed the OEM plugs replacement/ 040 gap.
You can see the live misfires on high end scanners.
[ATTACH=full]58454[/ATTACH]
Provides a count in live time, gives you an idea how bad it can be.
Mine was misfiring at part throttle 1650-1700 rpm and you could feel an engine shake, and then see it live.
TPS was sticking a bit due to worn tang in rear of TPS.
Throttle plate was also slightly binding, dremel polishing took place.
Might be worth a try to get one new mopar coil on #4
Fuel injector electronic pulses can be viewed on high end scanners if someone knows what they are doing as well.
I had no engine light. It takes a lot of misfires for it to turn the light on.
Ya clear the code and then run /drive it after clearing.

Excellent will try for now, thank you. If it comes back I will try and find someone who is more familiar with the platform. Any suggestions on a place in SoCal? More so Los Angeles?

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[tjkj2002]

Known issue for newer KJ's('05-'07) that have misfire codes that can not be felt due to the cat's starting to plug.

 

[K9JEEP]

Known issue for newer KJ's('05-'07) that have misfire codes that can not be felt due to the cat's starting to plug.

I have seen that mentioned a few other places as well. Would the cat start to clog with only 38k miles? Or would it clog from unburnt fuel?

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[tjkj2002]

I have seen that mentioned a few other places as well. Would the cat start to clog with only 38k miles? Or would it clog from unburnt fuel?

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Yes,basically from lack of use since it's a 10 year old vehicle with only 38,000 miles.

 

[K9JEEP]

Gotcha. What do you recommend?

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[HoosierJeeper]

Probably going to need new cats. Mopar ones flow the best and are 50 state legal obviously...which might be your only option to get it to pass emissions.

 

[K9JEEP]

I have driven 6 miles since getting the code cleared and it hasn't came on and could just be me but feels like it has a tad more pep.

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[K9JEEP]

So you recommend a whole exhaust system? I just passed smog and I have friend with a shop so not worried there, just don't want a damn misfire. I got this KJ to daily and get out of my car payment with my 2013 GTI, I really plan to care for this as much as I need to.

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[HoosierJeeper]

Just the cats is all I would do.

But...we don't even know for sure if that's the issue. What I would do is see if it comes back and then switch the coils around and see if it follows.

 

[K9JEEP]

You're right, sounds good. I'll report back, thanks for all your help fellas.

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[Logan Savage]

I'm asking because I'm curious , why would a cat problem only cause a misfire on # 4 cylinder ?

 

[J33Pfan]

IMO: just use the car. Get a fresh full tank of Higher octane fuel and drive the misfire out of it! Cause Carbon buildup causes misfires too!

try a quality fuel additive.

 

[K9JEEP]

I think a clogged cat would not allow the exhaust gases to flow out properly which would inturn would back up ignition and combustion, I think.
I don't know if it's in my head but it feels a bit stronger now. I'm going to keep driving it and deal with it as it comes. I'll report back.

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